Submitted by vivek on Thu, 10/20/2011 - 13:36
The below code will Disable Submit button onclick after page validation
string var = ClientScript.GetPostBackEventReference(btnSubmit, "").ToString();
btnSubmit.Attributes.Add("onClick", "javascript :if ( Page_ClientValidate() ){this.disabled=true; this.value='Please Wait...';" + var + "};");