How to display an error message box in a web application asp.net c#

Question

I have an ASP.NET web application, and I wanted to know how I could display an error message box when an exception is thrown.

For example,

Answer 1

You cannot just call messagebox.write cause you are disconnected from the client. You should register javascript code that shows a messagebox:

this.RegisterClientScriptBlock(typeof(string), "key",  string.Format("alert('{0}');", ex.Message), true);