Show data in comboBox window application through sqlserver connectivity using App.config file in ASP.Net with C#

*These namespaces are must be required for SqlServer Connectivity in your web form:-

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

App.config File

<?xml version="1.0" encoding="utf-8" ?>

<configuration>

  <configSections>

  </configSections>

  <appSettings>

    <add key="ConnectionString" value="Data Source=PRADEEP-HP;Initial Catalog=Decofloore2;User ID=User_006;Password=user006"/>

  </appSettings>

</configuration>

Form1.cs

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

namespace DemoWindowApplication

{

    public partial class Form3 : Form

    {   

        public Form3()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

            #region ddlList

            string StrCon = ConfigurationManager.AppSettings["ConnectionString"];

            SqlConnection SqlCon = new SqlConnection(StrCon);

            string SqlQuery = "Select ID,UserName,Address from Contectus";

            SqlCommand SqlComm = new SqlCommand(SqlQuery, SqlCon);

            SqlCon.Open();

            SqlDataReader dr;

            dr = SqlComm.ExecuteReader();

            BindingSource bs = new BindingSource();

            bs.DataSource = dr;

            comboBox1.DataSource = bs;

            comboBox1.DisplayMember = "UserName";

            comboBox1.ValueMember = "ID";

            comboBox1.Text = "       -------Name-------";

            #endregion

        }

    }

}

https://www.youtube.com/channel/UCKLRUr6U5OFeu7FLOpQ-FSw/videos