MessageBox.Show not working in ASP.Net

Here Mudassar Ahmed Khan has explained with an example, why MessageBox.Show does not work i.e. does not display messages in ASP.Net. ASP.Net is a Client Server technology where the program runs on Server while Page is displayed on Client in a Browser, while MessageBox.Show function is a Windows Forms function and hence when used in ASP.Net it displays Message Box on Server. Thus in ASP.Net, the messages needs to be displayed with the help of JavaScript Alert Message Box where JavaScript is a Client Side script which runs within Browser.