How to display messagebox in asp.net 3.5?

There are many ways to show or display message. I have two ways:

First way is this,

ScriptManager.RegisterStartupScript(this, this.GetType(), "onclick", "alert('" + message + "');", true); 

Second way is this,

String scriptString = "<script language=JavaScript>";

scriptString += "alert('" + message + "')";

scriptString += "</script>";

this.ClientScript.RegisterStartupScript(this.GetType(), "onlick", scriptString);

Hope my blog helps you.