Asp.net: Set default value in dropdownlist from code behind

In this article I am going to explain how to set the default value in dropdownlist from code behind in asp.net using C# and vb.net

Implementation:

I have created a table Tb_Country and insert dummy data.

ID	int
CountryName	varchar(100)

HML Markup:

<asp:DropDownList ID="DropDownList1" runat="server" CssClass="dropdownlist" AutoPostBack="true">

 </asp:DropDownList>

Import the namespace:

C# code:

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

VB.net Code:

Imports System.Data

Imports System.Data.SqlClient

Imports System.Configuration

Set default value in Dropdownlist

Create a method/function to populate the dropdown with default value and call it on page load. A default item is inserted at first position.

C# Code:

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["connection"].ToString());

    protected void Page_Load(object sender, EventArgs e)

    {      

        if (!IsPostBack)

        {

           Populatedropdown();

        }     

    }

  

 public void Populatedropdown()

    {       

        try

        {

            SqlCommand cmd = new SqlCommand("SELECT * FROM Tb_Country", con);

            DataTable dt = new DataTable();

            SqlDataAdapter adp = new SqlDataAdapter();

            adp = new SqlDataAdapter(cmd);

            adp.Fill(dt);

            DropDownList1.DataSource = dt;

            DropDownList1.DataTextField = "CountryName";

            DropDownList1.DataValueField = "ID";

            DropDownList1.DataBind();

            DropDownList1.Items.Insert(0,new ListItem("--Select City--","-1"));

        }

        catch (Exception ex)

        {

            Response.Write(ex.Message.ToString());

        }      

    }

VB.net Code:

Private con As New SqlConnection(ConfigurationManager.ConnectionStrings("connection").ToString())

    Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load

        If Not IsPostBack Then

            Populatedropdown()

        End If

    End Sub

Public Sub Populatedropdown()

        Try

            Dim cmd As New SqlCommand("SELECT * FROM Tb_Country", con)

            Dim dt As New DataTable()

            Dim adp As New SqlDataAdapter()

            adp = New SqlDataAdapter(cmd)

            adp.Fill(dt)

            DropDownList1.DataSource = dt

            DropDownList1.DataTextField = "CountryName"

            DropDownList1.DataValueField = "ID"

            DropDownList1.DataBind()

            DropDownList1.Items.Insert(0, New ListItem("--Select City--", "0"))

        Catch ex As Exception

            Response.Write(ex.Message.ToString())

        End Try

    End Sub