To show a message box from the ASP.NET page code behind, we could try to ways:

1. When no Ajax is used:

   • Response.Write("<script>alert('The Class has been created.');</script>");

2. When Ajax is used:

   • ScriptManager.RegisterStartupScript(this, this.GetType(), "Key", String.Format("alert('The {0} Class has been approved.');", Detail.Title), true);