to add 2 textbox value show in another textbox without using

try this code:

in aspx:


           
               
               
           
           
               
               
           
           
               
               
           
       

a
b	AutoPostBack="true" OnTextChanged="TextBox2_TextChanged">
a+b

in .cs:


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

public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void TextBox2_TextChanged(object sender, EventArgs e)
    {
        float amm = (float.Parse(TextBox1.Text) + float.Parse(TextBox2.Text));
        TextBox3.Text = Convert.ToString(amm);
    }
}