How to implement pop-up prompts dialog box in asp.net

In C #, the Code for the pop-up window is:

MessageBox ("User name or password is wrong!", "error:");

In ASP.net, this is not the way to do this, when we can write a class message (name casually), the contents are as follows:

//---------------------------------------
The writer: go begging tomorrow
qq:305725744
//---------------------------------------

Using System;

Namespace Common
{
<summary>
A summary description of the message.
</summary>
public class Message
{
Public message ()
{
//
TODO: Add constructor logic here
//
}

Returns a pop-up window
public static string Show (String strMsg)
{

Here 0 means strmsg this thing, 1 means/this thing.
Return String.Format ("<script language={1}javascript{1}>alert ({1}{0}{1});</script>", STRMSG, "/" ");
}
}
}

Then, on the page where you want to pop up the dialog box, add a Label control, assuming it is named Lblmsg, and then write the code in the background:

Lblmsg.text = Message.show ("Write the content to be bounced here");

This allows you to implement the pop-up prompts. Note that my class is written in the common layer, so I have to refer to the common layer first:

Using Common;

This method is actually provided in the purple language, when I wrote the project encountered this problem, he told me this method, thank him for his help.