ASP.NET Server Side Messages & Client Validation Message Handling.

using System;

namespace ValidationMessage
{
    public partial class ValidationSummary : BasePage
    {
        protected void Button1_Click(object sender, EventArgs e)
        {
            if(IsValid)
            {
             ShowSuccessMessage("All validation passed.");  
            }
            else
            {
                ShowErrorMessage("Validation failed.");
            }
        }
    }
}