How to find already exist customer id?

Hi Magesh,


Try this...

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Know_user_id_exits._Default" %>





   


   

   

    

       

       
    
   

   

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
namespace Know_user_id_exits
{
    public partial class _Default : System.Web.UI.Page
    {
        string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        SqlDataAdapter sqlda;
        SqlCommand com;
        string str;
        DataSet ds;

        protected void btn_add_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(connStr);
            con.Open();
            str = "select * from student";
            sqlda = new SqlDataAdapter(str, con);
            ds = new DataSet();
            sqlda.Fill(ds, "student");
            int newid;
            newid = Convert.ToInt32(txtid.Text.ToString());
            if (!checkIfUnique(newid))
            {
                Response.Write("ID Already exists!");
                txtid.Focus();
                return;
            }
            else
            {
                str = "insert into student values (" + txtid.Text + ",'" + txtname.Text + "','" + txtaddress.Text + "')";
                com = new SqlCommand(str, con);
                com.ExecuteNonQuery();

            }
            con.Close();
        }
        private bool checkIfUnique(int newid)
        {
            int oldid;
            foreach (DataRow r in ds.Tables["student"].Rows)
            {
                oldid = Convert.ToInt32(r["sid"]);
                if (oldid == newid)
                    return false;
            }
            return true;
        }
    }

}



Thanks
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