We can use Using keyword in following ways:1. Generally we use Using keyword when we add any namespace in our class, code-behind files.. Like: Using System.IO;2. Secondly we can use Using keyword when an object need to destroy automatically. It can be used in ADO.NET, Entity Framework, Web Service call. Here system automatically closes/disposes the object. Like: Using(WCFService cc = new WCFService()) {cc.method(); }