Hi PSowmiya,
Check this example. Now please take its reference and correct your code.
Database
I have made use of the following table Customers with the schema as follows.
I have already inserted few records in the table.
You can download the database table SQL by clicking the download link below.
Download SQL file
Code
Static Class to return items for populating ComboBox.
using System.Collections.Generic;
using System.Data.SqlClient;
public static class RetrieveModule
{
public static List<string> retrieveCountries()
{
List<string> countries = new List<string>();
SqlConnection conn = new SqlConnection(@"Data Source=.;Initial Catalog=Test;Uid=sa;pwd=pass@123;");
string Sql = "SELECT DISTINCT Country FROM Customers;";
SqlCommand cmd = new SqlCommand(Sql, conn);
conn.Open();
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
countries.Add(dr["Country"].ToString());
}
conn.Close();
return countries;
}
}
Accessing the static class in form
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
List<string> countries = RetrieveModule.retrieveCountries();
foreach (string country in countries)
{
cbCountries.Items.Add(country);
}
}
private void Submit(object sender, EventArgs e)
{
string message = "Country: " + cbCountries.Text;
MessageBox.Show(message);
}
}
Screenshot
