Track and search multiple orders using OrderIds in Multiline TextBox using ASP.Net

Using the Northwind database. I have created the following sample.

I am checking multiple Orders using OrderId in eachh line of TextBox and then displaying details in GridView

 <asp:TextBox ID="txtOrders" runat="server" TextMode = "MultiLine" style = "width:150px;height:100px">   
    </asp:TextBox>
    <br />
    <asp:Button ID="btnSearch" runat="server" Text="Search" OnClick = "Search" />
    <hr />
    <asp:GridView ID="GridView1" runat="server">
    </asp:GridView>

    private DataTable GetData(string query)
    {
        string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        SqlCommand cmd = new SqlCommand(query);
        using (SqlConnection con = new SqlConnection(conString))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;

                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    return dt;
                }
            }
        }
    }
    protected void Search(object sender, EventArgs e)
    {
        string orders = txtOrders.Text.Replace(Environment.NewLine, ",");
        string query = string.Format("select * from orders where orderId in ({0})", orders);
        GridView1.DataSource = GetData(query);
        GridView1.DataBind();
    }