code behind

    #region ICallbackEventHandler 成员

    protected string CallBackValue = string.Empty;

    string  ICallbackEventHandler.GetCallbackResult()

    {

        return  ValidateQuestion(CallBackValue).ToString();

    }

    void ICallbackEventHandler.RaiseCallbackEvent(string eventArgument)

    {

        this.CallBackValue = eventArgument;

    }

    #endregion

 private string  ValidateQuestion(string txtinputData)

    { 

    return "somthing error";

}

html:

function CallServer()

            {

                var txtinput=  document.all("txtinputdata").value;

                <%=ClientScript.GetCallbackEventReference(this,"txtinput","ReceiveServerData",null) %>;

            }

            function ReceiveServerData(rValue)

            {

                if(rValue.indexOf("False")!=-1)

                {

                    validatetxt= rValue.substr(6);

                    validateAnswerType=1;

                 }

            }