Set dynamically populated ASP.Net DropDownList selected Item using C# and VB.Net

Hi bhushan98,

Check this example. Now please take its reference and correct your code.

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

<asp:TextBox runat="server" ID="txtCountry" />
<asp:Button Text="Search" runat="server" OnClick="OnSearch" />
<hr />
<asp:DropDownList runat="server" ID="ddlCustomers" Width="220px">           
</asp:DropDownList>

Namespaces

C#

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

VB.Net

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

Code

C#

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

protected void OnSearch(object sender, EventArgs e)
{
    this.BindDropDownList();
}

private void BindDropDownList()
{
    SqlCommand cmd = new SqlCommand();
    cmd.CommandText = "SELECT CustomerID,ContactName FROM Customers WHERE Country = @Country OR @Country IS NULL ORDER BY ContactName ASC";
    cmd.Parameters.AddWithValue("@Country", !string.IsNullOrEmpty(txtCountry.Text) ? txtCountry.Text : (object)DBNull.Value);
    DataTable dt = GetData(cmd);
    ddlCustomers.DataSource = dt;
    ddlCustomers.DataTextField = "ContactName";
    ddlCustomers.DataValueField = "CustomerID";
    ddlCustomers.DataBind();
    ddlCustomers.Items.Insert(0, new ListItem { Text = "Select", Value = "0" });

    // Get value to be selected from datrabase.
    // Select using FindByText.
    if (ddlCustomers.Items.FindByText("Elizabeth Brown") != null)
    {
        ddlCustomers.ClearSelection();
        ddlCustomers.Items.FindByText("Elizabeth Brown").Selected = true;
    }
    // Select using FindByValue.
    if (ddlCustomers.Items.FindByValue("LONEP") != null)
    {
        ddlCustomers.ClearSelection();
        ddlCustomers.Items.FindByValue("LONEP").Selected = true;
    }
}

private DataTable GetData(SqlCommand cmd)
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    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;
            }
        }
    }
}

VB.Net

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

Protected Sub OnSearch(ByVal sender As Object, ByVal e As EventArgs)
    Me.BindDropDownList()
End Sub

Private Sub BindDropDownList()
    Dim cmd As SqlCommand = New SqlCommand()
    cmd.CommandText = "SELECT CustomerID,ContactName FROM Customers WHERE Country = @Country OR @Country IS NULL ORDER BY ContactName ASC"
    cmd.Parameters.AddWithValue("@Country", If(Not String.IsNullOrEmpty(txtCountry.Text), txtCountry.Text, CObj(DBNull.Value)))
    Dim dt As DataTable = GetData(cmd)
    ddlCustomers.DataSource = dt
    ddlCustomers.DataTextField = "ContactName"
    ddlCustomers.DataValueField = "CustomerID"
    ddlCustomers.DataBind()
    ddlCustomers.Items.Insert(0, New ListItem With {.Text = "Select", .Value = "0"})

    ' Get value to be selected from datrabase.
    ' Select using FindByText.
    If ddlCustomers.Items.FindByText("Elizabeth Brown") IsNot Nothing Then
        ddlCustomers.ClearSelection()
        ddlCustomers.Items.FindByText("Elizabeth Brown").Selected = True
    End If
    ' Select using FindByValue.
    If ddlCustomers.Items.FindByValue("LONEP") IsNot Nothing Then
        ddlCustomers.ClearSelection()
        ddlCustomers.Items.FindByValue("LONEP").Selected = True
    End If
End Sub

Private Function GetData(ByVal cmd As SqlCommand) As DataTable
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(conString)
        Using sda As SqlDataAdapter = New SqlDataAdapter()
            cmd.Connection = con
            sda.SelectCommand = cmd
            Using dt As DataTable = New DataTable()
                sda.Fill(dt)
                Return dt
            End Using
        End Using
    End Using
End Function

Screenshot