C# search using combobox and textbox

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using System.Data.SqlClient;
using System.Diagnostics;
using System.IO;

namespace testcsharp
{
    public partial class frmt3 : Form
    {
        public frmt3()
        {
            InitializeComponent();
        }

        connection cs = new connection();

        void columnitems(ComboBox cbo)
        {
            cbo.Items.Add("custid");
            cbo.Items.Add("name");
            cbo.Items.Add("gender");
            cbo.Items.Add("addr");
        }
        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                SqlConnection con = new SqlConnection(cs.getConnectionString());
                con.Open();
                string query = "select * from tblcustomer where column=@1 and value=@2";
                SqlCommand cmd = new SqlCommand(query, con);
                cmd.Parameters.AddWithValue("@1", txttblcolumn.Text);
                cmd.Parameters.AddWithValue("@2", txtvalue.Text);

                SqlDataReader dr = cmd.ExecuteReader();
                DataTable dt = new DataTable();

                if (dr.HasRows)
                {
                    dt = new DataTable();
                    dt.Load(dr);
                    dataGridView1.DataSource = dt;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

        private void frmt3_Load(object sender, EventArgs e)
        {
            columnitems(txttblcolumn);
        }
    }
}