Populate ASP.Net DropDownList based on TextBox first two characters using C# and VB.Net

Hi BugHunter,

Refer below sample.

HTML

Enter Text :
<asp:TextBox runat="server" ID="txtId" AutoPostBack="true" OnTextChanged="Filter" />
<br />
<asp:DropDownList runat="server" ID="ddlCountry">
</asp:DropDownList>

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

VB.Net

Imports System.Data.SqlClient
Imports System.Data

Code

C#

protected void Filter(object sender, EventArgs e)
{
    string orderId = txtId.Text.Substring(0, 5);
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT ShipCountry, OrderId FROM Orders WHERE OrderId = @OrderId",con))
        {
            cmd.Parameters.AddWithValue("@OrderId",orderId);
            using (SqlDataAdapter da = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                da.Fill(dt);
                ddlCountry.DataSource = dt;
                ddlCountry.DataTextField = "ShipCountry";
                ddlCountry.DataValueField = "OrderId";
                ddlCountry.DataBind();
            }
        }
    }
}

VB.Net

Protected Sub Filter(ByVal sender As Object, ByVal e As EventArgs)
    Dim orderId As String = txtId.Text.Substring(0, 5)
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ConnectionString)
        Using cmd As SqlCommand = New SqlCommand("SELECT ShipCountry, OrderId FROM Orders WHERE OrderId = @OrderId", con)
            cmd.Parameters.AddWithValue("@OrderId", orderId)
            Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                Dim dt As DataTable = New DataTable()
                da.Fill(dt)
                ddlCountry.DataSource = dt
                ddlCountry.DataTextField = "ShipCountry"
                ddlCountry.DataValueField = "OrderId"
                ddlCountry.DataBind()
            End Using
        End Using
    End Using
End Sub

Screenshot