.Net web services are built on XML-based standards for exchanging data. This means .NET web services can support only those data types that can be recognized by the XML schema standard. There are many proprietary .Net objects such as FileSteam, Eventlog etc. are not supported in the web services. These data types are .Net specific types that are not universally recognized, i.e. .Net specific only.
You can even exchange custom objects using .Net web services. The only limitation is that only public data members are transmitted, and all public members and properties must use one of the other supported data types.
You can use DataSet and DataTable to return information from database but can't use other ADO.NET objects such as DataColumns and DataRows.
.Net offers a distributed technology called .Net remoting that can plays around wide range of .Net specific data type. But unfortunately, .Net remoting doesn't support client other than .Net.
