Fill comboBox in C# Windows Form Application from Sql Database

Here in this post, I will show you how to fill / populate data to comboBox control from Sql database records in C# Windows Form Application.

The listbox will populated from database table using sqlDataReader.

Step 1: We will use the Customers table in Northwind database.

Step 2: In the next step, create a ComboBox control at design-time, you simply drag and drop a ComboBox control from Toolbox to a Form in Visual Studio.

Step 3:

Write a Namespace for connectivity as in the following code snippet.


using System.Data.SqlClient;

using System.Data.SqlClient;

Step 4: Define global variables.


SqlConnection con;
SqlCommand cmd;
SqlDataReader dr;

SqlConnection con;

SqlCommand cmd;

SqlDataReader dr;

Step 5: Create source code for Form_Load.


private void Form1_Load(object sender, EventArgs e)
        {
            con = new SqlConnection("server=.; Initial Catalog=Northwind;Integrated Security=SSPI");
            cmd = new SqlCommand();
            con.Open();
            cmd.Connection = con;
            cmd.CommandText = "SELECT * FROM Customers";
            dr = cmd.ExecuteReader();

            while (dr.Read())
            {
                comboBox1.Items.Add(dr["CompanyName"]);
            }
            con.Close();
        }

private void Form1_Load(object sender, EventArgs e)

{

con = new SqlConnection("server=.; Initial Catalog=Northwind;Integrated Security=SSPI");

cmd = new SqlCommand();

con.Open();

cmd.Connection = con;

cmd.CommandText = "SELECT * FROM Customers";

dr = cmd.ExecuteReader();

while (dr.Read())

{

comboBox1.Items.Add(dr["CompanyName"]);

}

con.Close();

}

Here are the all codes:


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace fill_comboBox
{
    public partial class Form1 : Form
    {
        SqlConnection con;
        SqlCommand cmd;
        SqlDataReader dr;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            con = new SqlConnection("server=.; Initial Catalog=Northwind;Integrated Security=SSPI");
            cmd = new SqlCommand();
            con.Open();
            cmd.Connection = con;
            cmd.CommandText = "SELECT * FROM Customers";
            dr = cmd.ExecuteReader();

            while (dr.Read())
            {
                comboBox1.Items.Add(dr["CompanyName"]);
            }
            con.Close();
        }
    }
}

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

using System.Data.SqlClient;

namespace fill_comboBox

{

public partial class Form1 : Form

{