Events of textbox or Javascript

Okay . This is easy enough. If you want to maintain it from Js You need to pass its CLientID. I am giving you an example.

This is my Js file. I have included this file in the Master Page. Have a look Please

var TestCal = {
    firstTextBoxID: "",
    secondTextBoxID: "",
    calTextBoxID: "",

    Initialize: function (submittedFirstTextBoxID, submittedSecondTextBoxID, submittedCalTextBox) {
        this.firstTextBoxID = submittedFirstTextBoxID;
        this.secondTextBoxID = submittedSecondTextBoxID;
        this.calTextBoxID = submittedCalTextBox;
    },

    Calculation: function () {

        var firstTextBoxValue = document.getElementById(this.firstTextBoxID).value;
        var secondTextBoxValue = document.getElementById(this.secondTextBoxID).value;
        var firstValue = parseInt(firstTextBoxValue != "" && firstTextBoxValue != "undefind" ? firstTextBoxValue : "0");
        var secondValue = parseInt(secondTextBoxValue != "" && secondTextBoxValue != "undefind" ? secondTextBoxValue : "0");
        var CalculatedValue = firstValue - secondValue;

        document.getElementById(this.calTextBoxID).value = CalculatedValue.toString();
    }
}

The aspx file is given below,

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeFile="Default.aspx.cs" Inherits="_Default" %>
 
<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">      
        <asp:TextBox  runat="server" ID="firstNumber" >
        <asp:TextBox runat="server" ID="secondNumber">
        <asp:TextBox  runat="server" ID="calculatedNumber" >  

And the .cs file is given below,

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {        
    }

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);

        if (!Page.ClientScript.IsStartupScriptRegistered(this.GetType(), "TestCall"))
        {
            Page.ClientScript.RegisterStartupScript(this.GetType(), "TestCall",
               "TestCal.Initialize('" + this.firstNumber.ClientID + "','" + this.secondNumber.ClientID + "','" + this.calculatedNumber.ClientID + "');", true);
        }

        string jsCalculation = "TestCal.Calculation()";
        firstNumber.Attributes.Add("OnKeyUp", jsCalculation);
        secondNumber.Attributes.Add("OnKeyUp", jsCalculation);
    }
}

Okay now run this and put value to fist two text boxes and the third one will display you the result. Here i didn't consider any validation. You need to do the validation in your own way.

add event to your text box

txtTwo.Attributes.Add("onchange", "Calculate();");

and add javascript to ur aspx page

<script type="text/javascript">

 function Calculate() {

 var txtOne = document.getElementById('txtValue1');
 var txtTwo = document.getElementById('txtValue2');
 var txtAns = document.getElementById('txtValueAns');
 txtAns.value=parseFloat(txtOne.value)-parseFloat(txtTwo.value);

       }

   </script>

call following javascript function on "onblur" of Textbox3.

<script>
  function getResult()
  {
   document.getElementById("textbox3").value =  eval(document.getElementById("textbox1").value) - eval(document.getElementById("textbox2").value);

return false;
  }
</script>

<script type="text/javascript" language="javascript">
      function SubstactData()
  {
    var txt1 = document.getElementById('<%=TextBox1.ClientID %>').value;
    var txt2 = document.getElementById('<%=TextBox2.ClientID %>').value;
    var txt3 = document.getElementById('<%=TextBox3.ClientID %>').value;

    document.getElementById('<%=TextBox3.ClientID %>').value = parseInt(txt1)+parseInt(txt2);
      }
</script>

Oh friends its not working....Is there is any need to enable 'Autopostback'?

Hello Am I enable 'Autopostback'?Its not working...

Aswathy
Am i change any other propery ?
The both code i written in aspx page but
still not working

add event to your Text box one and two:

txtTwo.Attributes.Add("onchange", "Calculate("+txtOne.clientId+","+txtTwo.clientId+","+txtThree.clientId+");");

Now In java script Write Calculate Method

function Calculate(txtOneId,txtTwoId,txtThreeId)
{
 var txtOne = document.getElementById(txtOneId);
 var txtTwo = document.getElementById(txtTwoId);
 var txtAns = document.getElementById(txtThreeId);
  //Put checks here
 txtAns.value=parseFloat(txtOne.value)-parseFloat(txtTwo.value);
}

<asp:Textbox Id="txtVal2" runat="server" OnLeave= "Javascript:SubstactValue();" /> 

<script>
  function SubstactValue()
  {
    var txt1 = document.getElementById('txtVal1');
    var txt2 = document.getElementById('txtVal2');
    var txt3 = document.getElementById('txtVal3');
 
    txt3.value =  parseInt(txt1.value) - parseInt(txt2.value);
  }
</script>