C#

mVerbs = new DesignerVerbCollection();
mVerbs.Add(new DesignerVerb("Add PropertyPane",
    new EventHandler(OnAddPane)));
mVerbs.Add(new DesignerVerb("Add PropertyPane as child",
    new EventHandler(OnAddPaneAsChild)));
mVerbs.Add(new DesignerVerb("Remove PropertyPane",
    new EventHandler(OnRemovePane)));
mVerbs[2].Enabled = false;

client.Credentials = new System.Net.NetworkCredential(username, password);

System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient([Host], [Port]);
smtp.Credentials = new System.Net.NetworkCredential([UserName], [Password]);

<system.net>
	<mailSettings>
		<smtp>
			<network host="" port="" userName="" password="" />
		</smtp>
	</mailSettings>
</system.net>

 private void comboBox3_SelectedIndexChanged(object sender, EventArgs e)
        {
            try
            {

                database = new OleDbConnection(connectionString);

                // Create a command object and then a query which accepts a papameter
                System.Data.OleDb.OleDbCommand cmd = new System.Data.OleDb.OleDbCommand("Select distinct ProductName from Products", database);
                database.Open();
                System.Data.OleDb.OleDbDataReader dr;
                dr = cmd.ExecuteReader();

                while (dr.Read())
                {
                    //comboBox3.Items.AddRange(new object[] { dr[1].ToString() });  //Change the index according to the values you want to populate in the combobox.
                    comboBox3.Items.AddRange(new Object[] { dr[1].ToString() });
                    
                }
                dr.Close();
            }
            catch (Exception ex)
            {

                MessageBox.Show(ex.Message);
                return;
            }
}