How to populate comboBox in windows form c#

ComboBox is a collection, in which we can take Text as well as value of the text. After array, developer designed comboBox or DropDownList because array contains one attribute of object, its does not take two value at a time. Suppose you want to store employee name and age into memory. Where we would not use array. Here we will bind the comboBox in different manner like
Method-1 : Bind ComboBox from dataset and datatable using ADO.NET
Method-2 : Bind ComboBox using Entity framework.

Method-1

I have a database table like Students, which take some value. The Data View of table, which is stored in database.

C# Code for binding ComboBox (Binding from DataReader)

using System;
using WindowsFormsApplication10;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.Entity;
using System.Data.SqlClient;

namespace WindowsFormsApplication10
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{

SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=(LocalDB)\\v11.0; Initial Catalog=STUDENTer; Integrated Security=true";
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "select * from Students";
cmd.Connection = con;
SqlDataReader rd = cmd.ExecuteReader();
while (rd.Read ())
{
string name = rd.GetString(1);
comboBox1.Items.Add(name);

}

}
}
}

Binding from DataTable

private void Form1_Load(object sender, EventArgs e)
{

SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=(LocalDB)\\v11.0; Initial Catalog=STUDENTer; Integrated Security=true";
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "select * from Students";
cmd.Connection = con;
SqlDataReader rd = cmd.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(rd);
comboBox1.DataSource = dt;
comboBox1.DisplayMember = "name";

}

Binding from DataSet

private void Form1_Load(object sender, EventArgs e)
{

SqlConnection con = new SqlConnection();
con.ConnectionString = "Data Source=(LocalDB)\\v11.0; Initial Catalog=STUDENTer; Integrated Security=true";
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "select * from Students";
cmd.Connection = con;
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
comboBox1.DataSource = ds.Tables[0];
comboBox1.DisplayMember = "name";

}

Method-2

If you want to bind combobox using entity framework or you can say strong model binding, just follow my steps.
Step-1 : One class, which name as "Student.cs", which works as database table.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WindowsFormsApplication10
{
public class Student
{
public int Id { get; set; }
public string name { get; set; }
}
}
In this class we are taking two member first is Id and second is name.
Step-2 : Take another class, which name as "DataContext", which is used for creating database also used for inserting table in it. Look like

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;

namespace WindowsFormsApplication10
{
class DataContext: DbContext
{
public DataContext() :
base("connectionstring1")
{

}
public DbSet<Student> Students { get; set; }

}
}

In this code, DataContext class inherited from DbContext class. Base class constructor create database using conectionstring, which is defined in App.Config file. like

<connectionStrings>

<add name="connectionstring1" providerName="System.Data.SqlClient" connectionString="Data Source=(LocalDB)\v11.0; Initial Catalog=STUDENTer; Integrated Security=true" />

</connectionStrings>

Step-3 : Add ComboBox control on form
Step-4 : Copy this code and paste into your form load event
private void Form1_Load(object sender, EventArgs e)
{
DataContext dc=new DataContext();
var stu = from student in dc.Students
select new
{
student.name
};
comboBox1.DataSource = stu.ToList();
comboBox1.DisplayMember = "name";

}