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Anonymous Methods In C#

In .net 2.0 you can declare a method inside of another piece of code, where a delegate is expected. This embedded method is called the anonymous method.

Example

public class AnonymousDelegate: Page {
	public AnonymousDelegate() {
		btnSubmit.Click += new EventHandler(btnSubmit_Click);
	}

	private void btnSubmit_Click(object sender, EventArgs e) {
		// ... Code         
	}
}

In this example, btnSubmit_Click method is defined outside the AnonymousDelegate() method. This code can be re-written as: -

public class AnonymousDelegate: Page {
	protected void Page_Init(object sender2, EventArgs e2) {
		//       Anonymous method
		btnSubmit.Click += delegate(object sender, EventArgs e) {...Code
		};
	}
}

Anonymous delegates can access all the private and public members of the containing procedure. Even an anonymous method can access the local variables of the containing procedure.

public class AnonymousDelegate: Page {
	protected void Page_Init(object sender2, EventArgs e2) {
		string str = "Test";
		//       Anonymous method
		btnSubmit.Click += delegate(object sender, EventArgs e) {
			Response.Write(str);
		};
	}
}

Here C# compiler creates a new class that nests inside the AnonymousDelegate class. It adds an anonymous method inside the new class along with the private member variable str.

Attaching Event To The Delegate

public class AnonymousDelegate: Page {
	protected void Page_Init(object sender2, EventArgs e2) {
		string str = "Test";
		//       Anonymous method        
		EventHandler clickHandler = delegate(object sender, EventArgs e) {
			Response.Write(str);
		};
	}
	button1.Click += clickHandler;
	button2.Click += clickHandler;
}

Posted By -	Karan Gupta

Posted On -	Thursday, January 21, 2010

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