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Pass Multiple Models And Anonymous Types To View In ASP.NET MVC

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Developers new to ASP.NET MVC often ask these questions:

  • How do I pass multiple models to a view?
  • How do I pass anonymous objects to a view?

This article provides a solution to both of these questions. Before we discuss the solution, let's quickly understand these questions and possible solutions in brief.

How do I pass multiple models to a view?

Consider a case where you have two model classes - Customer and Order. ASP.NET MVC allows you to pass only ONE model to a view. You typically do that by passing the model as a View() method parameter. This means a view can be bound with one and only one model. So, in the preceding example a view can either display Customer data or Order data. What if a view requires to display both? You can tackle such a situation as follows:

  • Create a new view model class, say CustomerOrder, that has two properties. One for holding Customer data and other for holding Order data.  
    public class CustomerOrder
{
  public List<Customer> Customers{get; set;}
  public List<Order> Orders{get; set;}
}
  • Pass one of the model as the View() method parameter and other(s) through ViewData or ViewBag.
  • Use ExpandoObject to create a dynamic model.

The first two approaches are quite straightforward and hence I won't discuss them here. Out of these three the first solution (custom view model class) is a recommended approach to deal with the situation. However, it calls for creating of a new view model class (POCO). The second one does the job but the view can't be strongly typed because models passed through ViewData or ViewBag are not part of the Model property of the view. The third approach is the topic of this article and is discussed in detail in the later part of this article.

 How do I pass anonymous objects to a view?

Sometimes you need to write LINQ to Entities queries that return data filled in an anonymous type. Consider the following example:

var query = from c in db.Customers
            join o in db.Orders
            on c.CustomerID equals o.CustomerID
            orderby c.CustomerID ascending
            select new { 
                c.CustomerID,
                c.CompanyName,
                o.OrderID,
                o.OrderDate 
            };

Here, you are not selecting Customer objects (select c). You are creating an anonymous type that has four properties - CustomerID, CompanyName, OrderID and OrderDate. Although this LINQ query works without any problem, the problem is you can't pass anonymous types to an ASP.NET MVC view. If you try to do so, you will see a runtime error. Of course, just like previous case you can create a new view model (POCO with these four properties) and project your data in it. You can then pass the collection to the View() method. As before this is a recommended solution but again you need create an additional class. If you wish to avoid doing that for some reason, here also you can resort to ExpandoObject. You can store the realized data in an ExpandoObject and then pass it to the view.

ExpandoObject to the rescue

The ExpandoObject class resides in System.Dynamic namespace and represents an object whose members can be dynamically added and removed at run time. In our specific cases an ExpandoObject can act as a container for multiple pieces of data that you wish to pass as a model to a view. So, in a way ExpandoObject is a "dynamic" alternative to a manually created view model.

Storing data in an ExpandoObject is straightforward.

dynamic model = new ExpandoObject();
model.Customers = <some_data_here>;
model.Orders = <some_data_here>;

The above code creates an instance of ExpandoObject class. Notice that the instance is stored in a variable of type dynamic. The code then assigns Customers and Orders properties of the ExpandoObject to some data. You should be familiar with this usage because ViewBag uses the same "dynamic" mechanism to store values.

Ok. Now that you know what an ExpandoObject is and how to use it, let's put it to use in our specific situations.

Let's assume that you have two model classes - Customers and Orders - as a part of Entity Framework data model. You wish to pass both of them to a view. So, you can write something like this in an action method:

public ActionResult Index()
{
    NorthwindEntities db=new NorthwindEntities();

    dynamic model = new ExpandoObject();
    model.Customers = db.Customers.ToList();
    model.Orders = db.Orders.ToList();
    return View(model);
}

Notice the code marked in bold letters. The code creates an ExpandoObject and assigns two properties on it - Customers and Orders. These properties store a generic List of the respective model objects. The ExpandoObject is then passed to the View() method.

You can use  the ExpandoObject in the view as shown below:

@model dynamic

...
<h1>List of Customers</h1>
<div>
  @foreach(var item in Model.Customers)
  {
    <h2>@item.CustomerID</h2>
  }
</div>

Notice that the view is marked to use a dynamic model using the @model dynamic line. This line is optional. If you don't write any @model then Razor defaults to dynamic. The foreach loop then iterates through Model.Customers property and displays all the CustomerIDs. Note that since Model points to an ExpandoObject, you won't get any IntelliSense help for the property names. You will need to key them in yourself. On the same lines you can display Model.Orders data.

Store anonymous objects in an ExpandoObject

In the preceding example you stored List of Customer and Order objects respectively in the model ExpandoObject. Now let's see how to store an anonymous object in an ExpandoObject.

var addtionalInfo = new { 
                    CustomersNote="This is a customer note",
                    OrdersNote="This is an order note" };
IDictionary<string, object> 
expandoAddInfo = new ExpandoObject();
foreach (PropertyDescriptor property 
         in 
         TypeDescriptor.GetProperties(addtionalInfo.GetType()))
{
    expandoAddInfo.Add(property.Name, 
           property.GetValue(addtionalInfo));
}
model.AdditionalInfo = expandoAddInfo;

The code creates an anonymous object with two properties - CustomersNote and OrdersNote - and stores it in additionalInfo variable. Then an ExpandoObject is created. This time, however, it is captured as an IDictionary<string, object>. Then a foreach loop iterates through all the properties of additionalInfo object. This is done using PropertyDescriptor and TypeDescriptor classes from System.ComponentModel namespace. These classes allow you to reflect upon the properties of any object (additionalInfo in this case). All the properties from the anonymous object are transferred to the ExpandoObject by adding them to the expandoAddInfo variable. Finally, AdditionalInfo property of model (which itself is an ExpandoObject) is set to expandoAddInfo ExpandoObject.

You can pass the model object to the view exactly as before. Once received in the view you can access the AdditionalInfo property as shown below:

<h1>Additional Information</h1>
<h2>@Model.AdditionalInfo.CustomersNote</h2>
<h2>@Model.AdditionalInfo.OrdersNote</h2>

What if you wish to convert a collection of anonymous objects to an ExpandoObject? The following code shows how this can be done:

var query = from c in db.Customers
            join o in db.Orders
            on c.CustomerID equals o.CustomerID
            orderby c.CustomerID ascending
            select new { 
                c.CustomerID,
                c.CompanyName,
                o.OrderID,
                o.OrderDate 
            };

List<ExpandoObject> joinData=new List<ExpandoObject>();

foreach(var item in query)
{
    IDictionary<string, object> itemExpando = new ExpandoObject();
    foreach (PropertyDescriptor property 
             in 
             TypeDescriptor.GetProperties(item.GetType()))
    {
        itemExpando.Add(property.Name, property.GetValue(item));
    }
    joinData.Add(itemExpando as ExpandoObject);
}

model.JoinData = joinData;

The above code is similar to the previous case but deals with a List of ExpandoObject (joinData variable). Each ExpandoObject (itemExpando variable) holds data belonging to a single anonymous object. The joinData List is then assigned to the JoinData property of the model ExpandoObject.

You can access JoinData inside a view as shown below:

<h1>Customer Orders Join Data</h1>
<div>
    @foreach (var item in Model.JoinData)
    {
        <h2>@item.CustomerID (@item.OrderID on @item.OrderDate)</h2>
    }
</div>

A note of caution about using ExpandoObject as shown above - Although ExpandoObject solves our problem, one should carefully evaluate whether there is any flaw in the model creation process. You should give a thought to creating POCOs for holding the multiple pieces instead of using an ExpandoObject. Since ExpandoObject instances are dynamic Visual Studio IntelliSense won't help much. POCO containers, on the other hand, give all the benefits of strongly typed view.

That's it for today! Keep coding!!

posted Oct 13, 2016 by Shivaranjini

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Customize View, Partial View And Layout Search Locations In ASP.NET MVC

By default ASP.NET MVC stores all the views associated to a controller inside a sub-folder of Views folder. On the same lines partial views and layout pages are stored inside Shared sub-folder under Views folder. Although this default arrangement works well in most of the cases, at times you may want to deviate from this convention based arrangement and store views, partial views and layouts in some different folder structure. Consider, for example, a huge application that wants to arrange partial views in several sub-folders inside Shared folder. Or some application may want to store views outside views folder. In such cases when you use view names in methods such as View(), Html.Partial() and PartialView() the system won't be able to find the required .cshtml files. Of course, you can use fully qualified paths in some cases but that makes your code rigid because any future change in the paths will require changes at multiple places.

Luckily, you can easily deal with the situation by creating a custom view engine. This article tells you how.

Let's assume that you wish to store partial views and layouts in the following custom folder structure:

image

Notice that partial views and layouts aren't stored directly inside Shared folder. They are stored inside PartialViews and Layouts sub-folders of Shared folder. Views are stored as per default convention. Let's assume that Index view uses Test.cshtml like this:

@Html.Partial("Test")

If you run the application under these settings, you will get this error in the browser:

image

As you can see, the system is unable to find Test.cshtml residing inside PartialViews sub-folder.

To deal with this situation you can create a custom view engine and then supply the custom search locations to the new view engine. Don't worry. Creating a custom view engine to accomplish this task is quite straightforward. Let's do that now.

Add a new class to your project and give it whatever name you wish to give to the new view engine. In my code I am calling my view engine as BinaryIntellectViewEngine. The complete class is shown below:

public class BinaryIntellectViewEngine : RazorViewEngine
{
    public BinaryIntellectViewEngine()
    {
        string[] locations = new string[] {  
            "~/Views/{1}/{0}.cshtml",  
            "~/Views/Shared/PartialViews/{0}.cshtml",  
            "~/Views/Shared/Layouts/{0}.cshtml"
        };

        this.ViewLocationFormats = locations;
        this.PartialViewLocationFormats = locations;
        this.MasterLocationFormats = locations;
    }
}

The BinaryIntellectViewEngine class inherits from RazorViewEngine base class. In our example we are using Razor view engine and hence the above code inherits from RazorViewEngine class. This inbuilt class comes from System.Web.Mvc namespace.

The magic that makes the custom locations work happens inside the constructor of the custom view engine class. Here, we create an array of strings. This array contains a list of all locations where the view engine should look for the views, partial views and layout pages. Notice the convention used in the paths. The placeholder {0} contains the view or payout page name whereas {1} contains the folder name (controller name).

The three base class properties namely ViewLocationFormats, PartialViewLocationFormats and MasterLocationFormats point to the list of search locations for views, partial views and layout pages respectively. In our example, all the three properties are set to the location string array.

This completes our custom view engine. The final step is to register this new view engine with the MVC framework. This is done inside Application_Start event in Global.asax.

void Application_Start(object sender, EventArgs e)
{
    AreaRegistration.RegisterAllAreas();
    GlobalConfiguration.Configure(WebApiConfig.Register);
    RouteConfig.RegisterRoutes(RouteTable.Routes);

    ViewEngines.Engines.Clear();
    ViewEngines.Engines.Add(new BinaryIntellectViewEngine());
}

The Application_Start event handler clears the existing registered view engines by calling Clear() method of ViewEngines.Engines collection. Then the new view engine is added using Add() method.

That's it! If you run the application now you should see the Test partial view rendered successfully.

image

 READ MORE
Perform List, Insert, Update And Delete In A Single View In ASP.NET MVC

A common way to perform list, insert, update and delete operations in ASP.NET MVC is to create four separate views. The List view forms the launching view where records are displayed and you can choose to Edit, Delete or Insert a record. However, in some cases you may want to perform all these operations in a single view itself. This task can be accomplished using full page postback or using Ajax. This article discusses the former technique.

Consider the following figure that shows one such arrangement:

image

The above figure shows a list of records from Customers table of Northwind database. You can Insert a new customer by clicking on Insert button. You can select a row for editing by clicking on the Select button. The selected customer is shown below the main table for editing. Similarly you can also delete a customer by clicking on the Delete button.

Model and View Model

Let's see how the above application can be built. Begin by creating a new empty ASP.NET MVCproject in Visual Studio. Then add an ADO.NET Entity Data Model for the Customers table. The Customer entity class is shown below:

image

Then add a new POCO to the Models folder and name it CustomersViewModel. As you will see later, this view model class will be passed from the HomeController to the Index view. The CustomersViewModel class is shown below:

public class CustomersViewModel
{
    public List<Customer> Customers { get; set; }
    public Customer SelectedCustomer { get; set; }
    public string DisplayMode { get; set; }
}

The CustomersViewModel class consists of three properties. The Customers property holds a List of Customer that are to be displayed on the view. The SelectedCustomer property points to a Customer that is selected by the user. If no Customer is selected this property is null. The DisplayMode property indicates the mode of the Customer details area. Possible values are ReadOnly (after selection), ReadWrite (during edit) and WriteOnly (during insert). For the sake of simplicity DisplayMode is created as a string property, you can easily make it to accept an enumeration.

Home controller and its action methods

Then add HomeController in the Controllers folder. The HomeController will contain the following action methods:

  • Index()
  • Select()
  • New()
  • Insert()
  • Edit()
  • Update()
  • Delete()
  • Cancel()

The method names are self-explanatory. All the actions except Index() are called as a result of POST operation. Let's discuss them briefly one by one.

public ActionResult Index()
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                m => m.CustomerID).Take(5).ToList(); 
        model.SelectedCustomer = null;
        return View(model);
    }
}

The Index() action fetches a list of customers and fills it in the Customers view model property. The SelectedCustomer is set to null because there is no selected customer in the beginning. Note that for the sake of simplicity the above code fetches only 5 customers. You can, of course, fetch all if you so wish.

[HttpPost]
public ActionResult New()
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                       m => m.CustomerID).Take(5).ToList();
        model.SelectedCustomer = null;
        model.DisplayMode = "WriteOnly";
        return View("Index", model);
    }
}

The New() action is called when a user hits the Insert button at the top of the page. It fills the Customers list as before. SelectedCustomer is set to null because a new record is to be added. The DisplayMode is set to WriteOnly because we will be accepting new customer details. The following figure shows how the insert area looks like:

image

[HttpPost]
public ActionResult Insert(Customer obj)
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        db.Customers.Add(obj);
        db.SaveChanges();

        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                         m => m.CustomerID).Take(5).ToList();
        model.SelectedCustomer = db.Customers.Find(obj.CustomerID);
        model.DisplayMode = "ReadOnly";
        return View("Index", model);
    }
}

The Insert() action is called when a user fills new customer details and clicks on the Save button (see above figure). It receives a Customer object as its parameter. Inside, the Insert() action adds that new Customer to the database. It also sets the currently selected customer to the newly added customer by setting the SelectedCustomer property. The DisplayMode is set to ReadOnly so that the record is displayed in read-only manner.

[HttpPost]
public ActionResult Select(string id)
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                    m => m.CustomerID).Take(5).ToList();
        model.SelectedCustomer = db.Customers.Find(id);
        model.DisplayMode = "ReadOnly";
        return View("Index",model);
    }
}

The Select() action method is called when the Select button from a customer table row is clicked. It receives CustomerID as its parameter. Inside, it fills Customers list as before. This time SelectedCustomer property is set to the Customer whose CustomerID is passed. The DisplayMode property is set to ReadOnly to indicate that the details of the selected customer should be displayed in a read-only table below the main customer listing (see below).

image

[HttpPost]
public ActionResult Edit(string id)
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                        m => m.CustomerID).Take(5).ToList();
        model.SelectedCustomer = db.Customers.Find(id);
        model.DisplayMode = "ReadWrite";
        return View("Index", model);
    }
}

The Edit() action is called when a user clicks on the Edit button once a Customer is selected. Inside, it sets the SelectedCustomer property to the Customer whose CustomerID is passed to the method. DisplayMode property is set to ReadOnly to display that record in editable table as shown below:

image

[HttpPost]
public ActionResult Update(Customer obj)
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        Customer existing = db.Customers.Find(obj.CustomerID);
        existing.CompanyName = obj.CompanyName;
        existing.ContactName = obj.ContactName;
        existing.Country = obj.Country;
        db.SaveChanges();
                
        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                      m => m.CustomerID).Take(5).ToList();

        model.SelectedCustomer = existing;
        model.DisplayMode = "ReadOnly";
        return View("Index", model);
    }
}

The Update() action is called when a user modifies an existing Customer data and clicks on the Save button (see above figure). Inside, the code updates an existing Customer and saves the changes back to the database. Then Customers, SelectedCustomer and DisplayMode properties of the view model are set.

[HttpPost]
public ActionResult Delete(string id)
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        Customer existing = db.Customers.Find(id);
        db.Customers.Remove(existing);
        db.SaveChanges();

        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                          m => m.CustomerID).Take(5).ToList();

        model.SelectedCustomer = null;
        model.DisplayMode = "";
        return View("Index", model);
    }
}

The Delete() action is called when Delete button in any of the customer row is clicked. It receives CustomerID as its parameter. Inside, it removes the specified Customer and saves the changes back to the database. The SelectedCustomer is set to null because post deletion that customer no longer exists in the database. For the same reason, DisplayMode is set to an empty string.

[HttpPost]
public ActionResult Cancel(string id)
{
    using (NorthwindEntities db = new NorthwindEntities())
    {
        CustomersViewModel model = new CustomersViewModel();
        model.Customers = db.Customers.OrderBy(
                          m => m.CustomerID).Take(5).ToList();
        model.SelectedCustomer = db.Customers.Find(id);
        model.DisplayMode = "ReadOnly";
        return View("Index", model);
    }
}

The Cancel() action is called when Cancel button from the Edit area is clicked. It receives CustomerID as its parameter. It changes the DisplayMode from ReadWrite to ReadOnly so that the SelectedCustomer is displayed in read-only fashion.

Notice that all the above action methods return Index view and CustomerViewModel object.

Index view

Now, let's see what goes inside the Index view.

@model MasterDetailsDemo.Models.CustomersViewModel

@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
    <style>
        .SelectedCustomer
        {
            background-color:gray;
            font-weight:bold;
        }
    </style>
</head>
<body>
    <h1>List of Customers</h1>

    <form method="post">
        <input type="submit" 
         value="Insert" formaction="/home/new" />
        <br /><br />
        <table border="1" cellpadding="10">
            <tr>
                <th>CustomerID</th>
                <th>CompanyName</th>
                <th colspan="2">Actions</th>
            </tr>
            @foreach (var item in Model.Customers)
            {
                if (Model.SelectedCustomer != null)
                {
                    if (item.CustomerID == 
                        Model.SelectedCustomer.CustomerID)
                    {
                        @:<tr class="SelectedCustomer">
                    }
                    else
                    {
                        @:<tr>
                    }
                }
                else
                {
                    @:<tr>
                }
                <td>@item.CustomerID</td>
                <td>@item.CompanyName</td>
                <td><input type="submit" 
                     formaction="/home/select/@item.CustomerID" 
                     value="Select" /></td>
                <td><input type="submit" 
                     formaction="/home/delete/@item.CustomerID" 
                     value="Delete" /></td>
                @:</tr>
            }
        </table>
    </form>
    <br /><br />
    @{
        if(Model.SelectedCustomer!=null)
        {
            if (Model.DisplayMode == "ReadOnly")
            {
                Html.RenderPartial
                ("ShowCustomer",Model.SelectedCustomer);
            }
            if (Model.DisplayMode == "ReadWrite")
            {
                Html.RenderPartial
                ("EditCustomer",Model.SelectedCustomer);
            }
        }
        if (Model.DisplayMode == "WriteOnly")
        {
            Html.RenderPartial("InsertCustomer",
            new MasterDetailsDemo.Models.Customer());
        }
    }
</body>
</html>

The Index view is divided into two logical parts. The top part displays a list of customers in a table. Notice that a CSS class SelectedCustomer is applied to the row that contains the selected CustomerID. The bottom part displays a Partial Page based on the value of DisplayMode. This way either show, insert or edit areas are displayed. Notice that there are three partial pages involved:

  • ShowCustomer.cshtml
  • EditCustomer.cshtml
  • InsertCustomer.cshtml

These three partial pages render the read-only, read-write and write-only displays respectively. All of them take Customer object as their model. Let's see each of these partial pages one by one.

ShowCustomer partial page

The following code shows ShowCustomer.cshtml partial page.

@model MasterDetailsDemo.Models.Customer

@using(Html.BeginForm("Edit","Home",FormMethod.Post))
{ 
<table border="1" cellpadding="10">
    <tr>
        <td>Customer ID :</td>
        <td>@Model.CustomerID</td>
    </tr>
    <tr>
        <td>Company Name :</td>
        <td>@Model.CompanyName</td>
    </tr>
    <tr>
        <td>Contact Name :</td>
        <td>@Model.ContactName</td>
    </tr>
    <tr>
        <td>Country :</td>
        <td>@Model.Country</td>
    </tr>
    <tr>
        <td colspan="2">
            <input type="submit" value="Edit" 
                   formaction="/home/edit/@Model.CustomerID" />
            <input type="submit" value="Cancel" 
                   formaction="/home/index" />
        </td>
    </tr>
</table>
}

Notice that the Edit and Cancel buttons submit to /home/edit and /home/index respectively. The other markup from the partial page is quite straightforward and displays CustomerID, CompanyName, ContactName and Country columns for a selected customer.

EditCustomer partial page

The following code shows what goes inside EditCustomer.cshtml:

@model MasterDetailsDemo.Models.Customer

@using (Html.BeginForm("Update", "Home", FormMethod.Post))
{
    <table border="1" cellpadding="10">
        <tr>
            <td>Customer ID :</td>
            <td>@Html.TextBoxFor(m => m.CustomerID, 
                         new { @readonly = "readonly" })</td>
        </tr>
        <tr>
            <td>Company Name :</td>
            <td>@Html.TextBoxFor(m => m.CompanyName)</td>
        </tr>
        <tr>
            <td>Contact Name :</td>
            <td>@Html.TextBoxFor(m => m.ContactName)</td>
        </tr>
        <tr>
            <td>Country :</td>
            <td>@Html.TextBoxFor(m => m.Country)</td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" value="Save" 
                       formaction="/home/update" />
                <input type="submit" value="Cancel" 
                       formaction="/home/cancel/@Model.CustomerID" />
            </td>
        </tr>
    </table>
}

Note that Save button and Cancel button submit to /home/update and /home/cancel respectively.

InsertCustomer partial page

Finally, here is the markup of InsertCustomer.cshtml:

@model MasterDetailsDemo.Models.Customer

@using (Html.BeginForm("Insert", "Home", FormMethod.Post))
{
    <table border="1" cellpadding="10">
        <tr>
            <td>Customer ID :</td>
            <td>@Html.TextBoxFor(m => m.CustomerID)</td>
        </tr>
        <tr>
            <td>Company Name :</td>
            <td>@Html.TextBoxFor(m => m.CompanyName)</td>
        </tr>
        <tr>
            <td>Contact Name :</td>
            <td>@Html.TextBoxFor(m => m.ContactName)</td>
        </tr>
        <tr>
            <td>Country :</td>
            <td>@Html.TextBoxFor(m => m.Country)</td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" value="Save" 
                       formaction="/home/insert" />
                <input type="submit" value="Cancel" 
                       formaction="/home/index" />
            </td>
        </tr>
    </table>
}

The Save and Cancel button submit to /home/insert and /home/index respectively.

That's it! All the parts of the application are in place. Run the application and test whether all the operations work as expected.

 READ MORE
Dealing With Multiple Instances Of Partial Views And Model Binding In ASP.NET MVC

ASP.NET model binding is quite powerful and flexible. It caters to most of the scenarios without much configuration from developers. However, at times you may need to intervene in order to achieve the desired model binding effect. One such situation is when you use multiple instance of a partial view on a view. This article shows one possible approach to deal with such situations.

Suppose that you have a web page as shown below:

image

As shown in the above figure the web page captures OrderID, CustomerID, ShippingAddress and BillingAddress from the end user. This information is stored in a model class - Order - that looks like this:

public class Order
{
    public int OrderID { get; set; }
    public int CustomerID { get; set; }

    public Address ShippingAddress { get; set; }
    public Address BillingAddress { get; set; }
}

public class Address
{
    public string Street1{get;set;}
    public string Street2{get;set;}
    public string Country{get;set;}
    public string PostalCode{get;set;}
}

The Order class consists of four public properties namely OrderID, CustomerID, ShippingAddress and BillingAddress. Notice that OrderID and CustomerID are integer properties whereas ShippingAddress and BillingAddress properties are of type Address. The Address class is also shown and consists of four string properties - Street1, Street2, Country and PostalCode.

Now let's assume that the whole page is rendered using two ASP.NET MVC Partial Pages. The OrderID and CustomerID is captured using _BasicDetails.cshtml as shown below:

@model Demo.Models.Order

<table>
    <tr>
        <td>@Html.LabelFor(m=>m.OrderID)</td>
        <td>@Html.TextBoxFor(m=>m.OrderID)</td>
    </tr>
    <tr>
        <td>@Html.LabelFor(m=>m.CustomerID)</td>
        <td>@Html.TextBoxFor(m=>m.CustomerID)</td>
    </tr>
</table>

Note that _BasicDetails partial page has its model set to Order class. The partial page then uses LabelFor() and TextBoxFor() helpers to display a label and textbox for the OrderID and CustomerID model properties respectively.

The address information is captured using _Address.cshtml as shown below:

@model Demo.Models.Address

<table>
    <tr>
        <td>@Html.LabelFor(m=>m.Street1)</td>
        <td>@Html.TextBoxFor(m=>m.Street1)</td>
    </tr>
    <tr>
        <td>@Html.LabelFor(m=>m.Street2)</td>
        <td>@Html.TextBoxFor(m=>m.Street2)</td>
    </tr>
    <tr>
        <td>@Html.LabelFor(m=>m.Country)</td>
        <td>@Html.TextBoxFor(m=>m.Country)</td>
    </tr>
    <tr>
        <td>@Html.LabelFor(m=>m.PostalCode)</td>
        <td>@Html.TextBoxFor(m=>m.PostalCode)</td>
    </tr>
</table>

The _Address partial page has Address class as its model and uses LabelFor() and TextBoxFor() helpers to display model properties.

The Index view that makes use of _BasicDetails and _Address partial pages to form the complete page is shown below:

@model Demo.Models.Order

...
@using(Html.BeginForm("ProcessForm","Home",FormMethod.Post))
{
  <h3>Basic Details</h3>
  @Html.Partial("_BasicDetails")

  <h3>Shipping Address</h3>
  @Html.Partial("_Address",Model.ShippingAddress)
        
  <h3>Billing Address</h3>
  @Html.Partial("_Address",Model.BillingAddress)
        
  <input type="submit" value="Submit" />
}
</body>
</html>

The Index view renders the _BasicDetails partial page using Partial() helper. Since the model for Index view is Order class, the same is available to the _BasicDetails partial page. Then two instances of _Address partial page are rendered on the page to capture ShippingAddress and BillingAddress respectively. Recollect that _Address has Address class as its model. So, Model.ShippingAddress and Model.BillingAddress are passed to the Partial() helper.

The above form submits to ProcessForm action method that looks like this:

public ActionResult ProcessForm(Order ord)
{
    //do something with Order object here
    return View("Index");
}

And the Index() action method looks like this:

public ActionResult Index()
{
    Order ord = new Order();
    ord.BillingAddress = new Address();
    ord.ShippingAddress = new Address();
    return View(ord);
}

Both of these methods are quite straightforward and need no explanation.

Now comes the important and tricky part. If you run the application at this stage, you will get the following HTML markup in the browser (unwanted markup has been removed for the sake of clarity):

<form action="/Home/ProcessForm" method="post">        
<h3>Basic Details</h3>
<table>
    <tr>
        <td><label for="OrderID">OrderID</label></td>
        <td><input id="OrderID" name="OrderID" type="text" /></td>
    </tr>
    <tr>
        <td><label for="CustomerID">CustomerID</label></td>
        <td><input id="CustomerID" name="CustomerID" type="text" /></td>
    </tr>
</table>
<h3>Shipping Address</h3>
<table>
    <tr>
        <td><label for="Street1">Street1</label></td>
        <td><input id="Street1" name="Street1" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="Street2">Street2</label></td>
        <td><input id="Street2" name="Street2" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="Country">Country</label></td>
        <td><input id="Country" name="Country" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="PostalCode">PostalCode</label></td>
        <td><input id="PostalCode" name="PostalCode" type="text" value="" /></td>
    </tr>
</table>
<h3>Billing Address</h3>
<table>
    <tr>
        <td><label for="Street1">Street1</label></td>
        <td><input id="Street1" name="Street1" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="Street2">Street2</label></td>
        <td><input id="Street2" name="Street2" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="Country">Country</label></td>
        <td><input id="Country" name="Country" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="PostalCode">PostalCode</label></td>
        <td><input id="PostalCode" name="PostalCode" type="text" value="" /></td>
    </tr>
</table>
<input type="submit" value="Submit" />
</form>

Notice the markup in bold letters. Can you see HTML elements with duplicate id and name attributes? That's because you are rendering two instance of the _Address partial page. The model binding framework requires that the HTML fields follow this naming convention for the model binding to work as expected:

<input id="ShippingAddress_Street1" 
       name="ShippingAddress.Street1" type="text" value="" />
<input id="BillingAddress_Street1" 
       name="BillingAddress.Street1" type="text" value="" />

As you can see from the above markup the id and name attributes must fully quality the model property being bound. In the absence of such a naming pattern the Order instance won't be bound as expected as confirmed by the following figure:

image

As shown above the ShippingAddress and BillingAddress properties are null whereas OrderID and CustomerID are captured successfully.

The above problem can be solved by using a variation of the Partial() helper while rendering the _Address partial page. The following code shows how this is done:

<h3>Basic Details</h3>
@Html.Partial("_BasicDetails")

<h3>Shipping Address</h3>
@Html.Partial("_Address", 
  new ViewDataDictionary() 
  { 
    TemplateInfo = new TemplateInfo() 
      { HtmlFieldPrefix = "ShippingAddress" } })

<h3>Billing Address</h3>
@Html.Partial("_Address", 
  new ViewDataDictionary() 
    { TemplateInfo = new TemplateInfo() 
      { HtmlFieldPrefix = "BillingAddress" } })

The variation of Partial() helper used above uses ViewDataDictionary parameter to specify TemplateInfo. The HtmlFieldPrefix property of the TemplateInfo is set to ShippingAddress for the first instance and to the BillingAddress for the second instance.

If you run the application now, you will find the following markup in the browser:

<form action="/Home/ProcessForm" method="post">
<h3>Basic Details</h3>
<table>
    <tr>
        <td><label for="OrderID">OrderID</label></td>
        <td><input id="OrderID" name="OrderID" type="text" value="0" /></td>
    </tr>
    <tr>
        <td><label for="CustomerID">CustomerID</label></td>
        <td><input id="CustomerID" name="CustomerID" type="text" value="0" /></td>
    </tr>
</table>
<h3>Shipping Address</h3>
<table>
    <tr>
        <td><label for="ShippingAddress_Street1">Street1</label></td>
        <td><input id="ShippingAddress_Street1" 
                   name="ShippingAddress.Street1" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="ShippingAddress_Street2">Street2</label></td>
        <td><input id="ShippingAddress_Street2" 
                   name="ShippingAddress.Street2" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="ShippingAddress_Country">Country</label></td>
        <td><input id="ShippingAddress_Country" 
                   name="ShippingAddress.Country" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="ShippingAddress_PostalCode">PostalCode</label></td>
        <td><input id="ShippingAddress_PostalCode" 
                   name="ShippingAddress.PostalCode" type="text" value="" /></td>
    </tr>
</table>
<h3>Billing Address</h3>
<table>
    <tr>
        <td><label for="BillingAddress_Street1">Street1</label></td>
        <td><input id="BillingAddress_Street1" 
                   name="BillingAddress.Street1" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="BillingAddress_Street2">Street2</label></td>
        <td><input id="BillingAddress_Street2" 
                   name="BillingAddress.Street2" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="BillingAddress_Country">Country</label></td>
        <td><input id="BillingAddress_Country" 
                   name="BillingAddress.Country" type="text" value="" /></td>
    </tr>
    <tr>
        <td><label for="BillingAddress_PostalCode">PostalCode</label></td>
        <td><input id="BillingAddress_PostalCode" 
                   name="BillingAddress.PostalCode" type="text" value="" /></td>
    </tr>
</table>
<input type="submit" value="Submit" />
</form>

As expected the id and name attributes are now fully qualified and hence the model binding will happen as expected as shown below:

image

The model binding now correctly captures ShippingAddress as well as BillingAddress information.

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View in ASP.NET MVC:

In this section, you will learn about the View in ASP.NET MVC framework.

View is a user interface. View displays data from the model to the user and also enables them to modify the data.

ASP.NET MVC views are stored in Views folder. Different action methods of a single controller class can render different views, so the Views folder contains a separate folder for each controller with the same name as controller, in order to accommodate multiple views. For example, views, which will be rendered from any of the action methods of HomeController, resides in Views > Home folder. In the same way, views which will be rendered from StudentController, will resides in Views > Student folder as shown below.

View folders for Controllers

View folders for Controllers

Note :Shared folder contains views, layouts or partial views which will be shared among multiple views.

Razor view engine:

Microsoft introduced the Razor view engine and packaged with MVC 3. You can write a mix of html tags and server side code in razor view. Razor uses @ character for server side code instead of traditional <% %>. You can use C# or Visual Basic syntax to write server side code inside razor view. Razor view engine maximize the speed of writing code by minimizing the number of characters and keystrokes required when writing a view. Razor views files have .cshtml or vbhtml extension.

ASP.NET MVC supports following types of view files:

View file extensionDescription
.cshtmlC# Razor view. Supports C# with html tags.
.vbhtmlVisual Basic Razor view. Supports Visual Basic with html tags.
.aspxASP.Net web form
.ascxASP.NET web control

Learn Razor syntax in the next section. Let's see how to create a new view using Visual Studio 2013 for Web with MVC 5.

Create New View:

We have already created StudentController and Student model in the previous section. Now, let's create a Student view and understand how to use model into view.

We will create a view, which will be rendered from Index method of StudentContoller. So, open a StudentController class -> right click inside Index method -> click Add View..

Create View

In the Add View dialogue box, keep the view name as Index. It's good practice to keep the view name the same as the action method name so that you don't have to specify view name explicitly in the action method while returning the view.

Select the scaffolding template. Template dropdown will show default templates available for Create, Delete, Details, Edit, List or Empty view. Select "List" template because we want to show list of students in the view.

View

 

Now, select Student from the Model class dropdrown. Model class dropdown automatically displays the name of all the classes in the Model folder. We have already created Student Model class in the previous section, so it would be included in the dropdown.

View

Check "Use a layout page" checkbox and select _Layout.cshtml page for this view and then click Addbutton. We will see later what is layout page but for now think it like a master page in MVC.

This will create Index view under View -> Student folder as shown below:

View

The following code snippet shows an Index.cshtml created above.

Views\Student\Index.cshtml:

@model IEnumerable<MVC_BasicTutorials.Models.Student>

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Index</h2>

<p>
    @Html.ActionLink("Create New", "Create")
</p>
<table class="table">
    <tr>
        <th>
            @Html.DisplayNameFor(model => model.StudentName)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.Age)
        </th>
        <th></th>
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.StudentName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Age)
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id=item.StudentId }) |
            @Html.ActionLink("Details", "Details", new { id=item.StudentId  }) |
            @Html.ActionLink("Delete", "Delete", new { id = item.StudentId })
        </td>
    </tr>
}

</table>

As you can see in the above Index view, it contains both Html and razor codes. Inline razor expression starts with @ symbol. @Html is a helper class to generate html controls. You will learn razor syntax and html helpers in the coming sections.

Index.cshtml

The above Index view would look like below.

create view in asp.net mvc

Index View

Note :Every view in the ASP.NET MVC is derived from WebViewPage class included in System.Web.Mvc namespace.

Points to Remember :

  1. View is a User Interface which displays data and handles user interaction.
  2. Views folder contains separate folder for each controller.
  3. ASP.NET MVC supports Razor view engine in addition to traditional .aspx engine.
  4. Razor view files has .cshtml or .vbhtml extension.
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Four Ways Of Handling Multiple Submit Buttons In ASP.NET MVC

A common beginner question is - How to handle multiple submit buttons in ASP.NET MVC?

In web forms this is quite straightforward because all you need to do is write the Click event handler of the respective buttons. However, in ASP.NET MVC you need to rely on the plain HTML and / or  JavaScript to deal with the situation. To that end this article illustrates four ways of handling multiple submit buttons.

The following code uses a simple Customer model class that looks like this:

public class Customer
{
    public string CustomerID { get; set; }
    public string CompanyName { get; set; }
    public string ContactName { get; set; }
    public string Country { get; set; }
}

The Index view accepts values for all the properties of the Customer classly CustomerID, CompanyName, ContactName and Country.

1. Multiple buttons with different names

In this technique you use BeginForm() helper as usual and submit a form to an action method. The relevant markup from the Index view that does this is shown below:

@model MultipleSubmitButtons.Models.Customer
...
...
@using (Html.BeginForm("ProcessForm", "Home", FormMethod.Post))
{
    @Html.EditorForModel()
    <br />
    <input type="submit" name="save" value="Save" />
    <input type="submit" name="cancel" value="Cancel" />
}

As you can see the BeginForm() helper specifies the action name to be ProcessForm, controller name to be Home and the form method to be POST. To display a data entry textboxes EditorForModel() helper is used. You can very well use helpers such as TextBoxFor() and LabelFor() if you so wish.

There are two submit buttons - one with name attribute set to save and the other with name of cancel. When you click a particular button, its name and value is sent to the server. The ProcessForm() action needs to grab these values to detect which one was clicked.

This is how the Index view looks like in the browser:

image

Th ProcessForm() action that does this detection is shown below:

[HttpPost]
public ActionResult ProcessForm(Customer obj,
                   string save,string cancel)
{
    if(!string.IsNullOrEmpty(save))
    {
        ViewBag.Message = "Customer saved successfully!";
    }
    if (!string.IsNullOrEmpty(cancel))
    {
        ViewBag.Message = "The operation was cancelled!";
    }
    return View("Result",obj);
}

Notice that the ProcessForm() action receives three parameters through model binding. The first parameter is the Customer object that holds the values entered in the textboxes. The save and cancel string parameters hold the value of the respective buttons. These parameter names must match the names of the butttons on the form. If a button is clicked, its value is received in the action. Otherwise its value will be null. For example, if you click on the Save button the save parameter will hold Save and the cancel parameter will hold null.

The if blocks then check the value of save and cancel parameters and accordingly set a ViewBag property. The ProcessForm() action returns Result view. The markup of Result view is shown below:

@model MultipleSubmitButtons.Models.Customer
...
<body>
    <h1>@ViewBag.Message</h1>
    @Html.DisplayForModel()
</body>
</html>

The Result view simply displays the Message property from the ViewBag and also displays the value held in the Customer object.

2. Multiple buttons with the same name

This technique is similar to the previous technique. But the buttons involved are given the same name in the HTML markup.

@using (Html.BeginForm("ProcessForm", "Home", FormMethod.Post))
{
    @Html.EditorForModel()
    <br />
    <input type="submit" name="submit" value="Save" />
    <input type="submit" name="submit" value="Cancel" />
}

Notice that the name attribute of both the buttons is set to submit and their value attribute is set to some string.

Then the ProcessForm action accepts a single parameter - submit - that receives the value of the button clicked by the user. This is shown below:

[HttpPost]
public ActionResult ProcessForm(Customer obj, string submit)
{
    switch(submit)
    {
        case "Save":
            ViewBag.Message = "Customer saved successfully!";
            break;
        case "Cancel":
            ViewBag.Message = "The operation was cancelled!";
            break;
    }
    return View("Result", obj);
}

As you can see the submit parameter is checked for its value. If you click the Save button, submit parameter will be Save. If you click on Cancel button the submit parameter will have alue of Cancel. The switch statement then checks the values and does some processing specific to a button.

3. HTML5 formaction and formmethod attributes

In this technique you use the formaction and formmethod attributes introduced in HTML5. These attributes can be set on the buttons under consideration. The formaction attribute indicates the form's action whereas the formpost attribute indicates the form submition method.

The modified form markup is shown below:

@using (Html.BeginForm())
{
    @Html.EditorForModel()
    <br />
    <input type="submit" name="save" value="Save" 
              formaction="SaveForm" formmethod="post" />
    <input type="submit" name="cancel" value="Cancel" 
              formaction="CancelForm" formmethod="post" />
}

As you can see the formaction attribute of the save button submits to SaveForm() action whereas the cancel button submits to the CancelForm() action. The formmethod attribute is set to post for both the buttons.

The SaveForm() and CancelForm() actions are shown below:

[HttpPost]
public ActionResult SaveForm(Customer obj)
{
    ViewBag.Message = "Customer saved successfully!";
    return View("Result", obj);
}

[HttpPost]
public ActionResult CancelForm(Customer obj)
{
    ViewBag.Message = "The operation was cancelled!";
    return View("Result", obj);
}

The SaveForm() needs to accept only the Customer model object because this is exclusively called by the save button. Similarly the CancelForm() action needs to receive only the model object since it is invoked exclusively by the cancel button. 

4. jQuery / JavaScript code

If above techniques doesn't meet your requirements you can always use jQuery or JavaScript to programatically set the form action. The following markup shows how the modified form looks like:

@using (Html.BeginForm())
{
    @Html.EditorForModel()
    <br />
    <input type="submit" id="save" value="Save" />
    <input type="submit" id="cancel" value="Cancel" />
}

This time the ID attribute of the buttons is set to save and cancel respectively. This way you can easily access them in the jQuery code. The jQuery code that wires the click event handlers for these buttons and sets the form action dynamically is shown below:

$(document).ready(function () {

    $("#save").click(function () {
        $("form").attr("action", "/home/saveform");
    });

    $("#cancel").click(function () {
        $("form").attr("action", "/home/cancelform");
    });

});

The click event handler of the save button sets the action attribute of the form to /home/saveform. This is done using the attr() method of jQuery. On the same lines the click event handler of the cancel button sets the action to /home/cancelform.

Which technique to use?

All the techniques discussed above are standard ways of dealing with multiple submit buttons. So, the selection depends on developers choice and application requirements. If your logic is such that a single action is doing multiple things then technique #1 comes handy. An example of this technique can be seenhere that develops a wizard with next and previous buttons. The second technique has a drawback that if you change the value attribute then you need to adjust the switch statement accordingly. Moreover, it may pose a problem in multilingual websites since you are checking the value displayed on the buttons. So, this technique should be avoided if you anticipate the button texts to change. If the target browser supports HTML5 (all the leading browsers support these attributes) then using formaction and formmethod attributes is recommended. This way you get a cleaner separatation of the concerns and the code is more readable. If the form or the buttons themselves are being generated on-the-fly then jQuery technique is handy because things are changing dynamically.

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