Up-Date record in SQL Database using C#.net

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net;
using System.Data;
using System.Data.SqlClient;

namespace WebApplication1
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button3_Click(object sender, EventArgs e)
        {
            SqlConnection cnn = new SqlConnection(@"Data Source=localhost\SQLExpress;Initial Catalog=awais;Integrated Security=True;Integrated Security=True ");
            cnn.Open();
string query = "update logout set name ='"+TextBox3.Text+"' where name = '" + TextBox2.Text + "';";
            SqlCommand cmd = new SqlCommand(query, cnn);
            cmd.ExecuteNonQuery();

            Response.Write("update  is done!");

        }

   
    }
}