Search Filter GridView Records based on TextBox in ASP.Net

Check this sample using Northwind database

Id:
    <asp:TextBox ID="txtSearch" runat="server"></asp:TextBox>
    <asp:Button ID="Button1" runat="server" Text="Search" OnClick = "Search" />
    <br />
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns = "false">
        <Columns>
            <asp:BoundField DataField="CustomerId" HeaderText="Contact Id" />
            <asp:BoundField DataField="ContactName" HeaderText="Contact Id" />
            <asp:BoundField DataField="Country" HeaderText="Country" />
        </Columns>
    </asp:GridView>

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindGrid();
}
}
    protected void Search(object sender, EventArgs e)
    {
        this.BindGrid();
    }
    private void BindGrid()
    {
        string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        string query = "SELECT * FROM Customers";

        string id = txtSearch.Text.Trim();
        if (!string.IsNullOrEmpty(id))
        {
            id = string.Format(" where CustomerId = '{0}'", id);
        }
        SqlCommand cmd = new SqlCommand(query + id);
        using (SqlConnection con = new SqlConnection(conString))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;

                sda.SelectCommand = cmd;
                using (DataSet ds = new DataSet())
                {
                    sda.Fill(ds);
                    GridView1.DataSource = ds;
                    GridView1.DataBind();
                }
            }
        }
    }