This is common requirement that- after doing some server side functionality we want to show alert message and then redirect to another page.
Here I am showing - How to redirect to another page after alert message?
Here is code-
Response.Write("<script> alert('Your Message.');window.location='TargetpageURL'; </script>");
Method 2: If you are using Ajax functionality on that case Response.Write() will not work then you can use this code-
ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "ScriptKey", "alert('Your Message.');window.location='TargetpageURL'; ", true);