Populate ASP.Net DropDownList with Selected Value from Database using C# and VB.Net

Hi landomarossi,

Please refer below sample.

Database

I have made use of the following table Customers with the schema as follows. 

I have already inserted few records in the table.

You can download the database table SQL by clicking the download link below.

Download SQL file

HTML

<asp:TextBox ID="txtId" runat="server"></asp:TextBox>
<asp:Button ID="btnGet" runat="server" Text="Send" OnClick="OnbtnGet" />
<hr />
<asp:TextBox ID="txtName" runat="server"></asp:TextBox><br />
<asp:DropDownList ID="ddlCountries" runat="server"></asp:DropDownList>

Namespaces

C#

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

VB.Net

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.BindDropDownList();
    }
}

private void BindDropDownList()
{
    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT Country FROM Customers", con))
        {
            con.Open();
            ddlCountries.DataSource = cmd.ExecuteReader();
            ddlCountries.DataTextField = "Country";
            ddlCountries.DataValueField = "Country";
            ddlCountries.DataBind();
            con.Close();
        }
    }
    ddlCountries.Items.Insert(0, new ListItem("---Select Country---", "0"));
}

protected void OnbtnGet(object sender, EventArgs e)
{
    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        using (SqlCommand cmd = new SqlCommand("Select Name,Country from Customers Where CustomerId=@CustomerId", con))
        {
            cmd.Parameters.AddWithValue("@CustomerId", txtId.Text);
            try
            {
                con.Open();
                SqlDataReader sdr = cmd.ExecuteReader();
                if (sdr.Read())
                {
                    txtName.Text = sdr["Name"].ToString();
                    if (ddlCountries.Items.FindByValue(sdr["Country"].ToString()) != null)
                    {
                        ddlCountries.ClearSelection();
                        ddlCountries.Items.FindByValue(sdr["Country"].ToString()).Selected = true;
                    }
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                con.Close();
            }

        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.BindDropDownList()
    End If
End Sub

Private Sub BindDropDownList()
    Dim constring As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constring)
        Using cmd As SqlCommand = New SqlCommand("SELECT Country FROM Customers", con)
            con.Open()
            ddlCountries.DataSource = cmd.ExecuteReader()
            ddlCountries.DataTextField = "Country"
            ddlCountries.DataValueField = "Country"
            ddlCountries.DataBind()
            con.Close()
        End Using
    End Using

    ddlCountries.Items.Insert(0, New ListItem("---Select Country---", "0"))
End Sub

Protected Sub OnbtnGet(ByVal sender As Object, ByVal e As EventArgs)
    Dim constring As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constring)
        Using cmd As SqlCommand = New SqlCommand("Select Name,Country from Customers Where CustomerId=@CustomerId", con)
            cmd.Parameters.AddWithValue("@CustomerId", txtId.Text)
            Try
                con.Open()
                Dim sdr As SqlDataReader = cmd.ExecuteReader()
                If sdr.Read() Then
                    txtName.Text = sdr("Name").ToString()
                    If ddlCountries.Items.FindByValue(sdr("Country").ToString()) IsNot Nothing Then
                        ddlCountries.ClearSelection()
                        ddlCountries.Items.FindByValue(sdr("Country").ToString()).Selected = True
                    End If
                End If
            Catch ex As Exception
                Throw ex
            Finally
                con.Close()
            End Try
        End Using
    End Using
End Sub

Screenshot