MessageBox like function in ASP.NET

Question

Sir, could you tell me a solution for a MessageBox like function in ASP.NET.

I know to handle this function with Label Control. So not need this.

I want a function same as Messagebox.

The function is not a first calling form database, calling from SPclass into .aspx.cs class.

So the function to invoke MessageBox to be write in SP class.

if you had any doubt on my question, ask .Otherwise, give solution.