protected void Page_Load(object sender, EventArgs e) 
    { 
      PostBackOptions options = new PostBackOptions(Button1,string.Empty); 
   
      StringBuilder sb = new StringBuilder(); 
      if (Button1.CausesValidation && this.GetValidators(Button1.ValidationGroup).Count > 0) 
      { 
        options.ClientSubmit = true; 
        options.PerformValidation = true; 
        options.ValidationGroup = Button1.ValidationGroup; 
   
        sb.Append("if (typeof(Page_ClientValidate) == 'function')"); 
        sb.Append("if(Page_ClientValidate(\"" + Button1.ValidationGroup + "\")==false) return false;"); 
      } 
      if (!string.IsNullOrEmpty(Button1.PostBackUrl)) 
        options.ActionUrl = HttpUtility.UrlPathEncode(Button1.ResolveClientUrl(Button1.PostBackUrl)); 
       
      sb.Append("this.disabled = true;"); 
      sb.Append(ClientScript.GetPostBackEventReference(options)); 
      sb.Append(";"); 
      Button1.Attributes.Add("onclick", sb.ToString()); 
    }