connecting data from table to combo box c#

Question

I am trying to display data from a table into a combo box(usernames in a combo box) but i sorted most errors that i got . "my error"

System.InvalidCastException: Specified cast is not valid.

also i only get this message when i debug the program and open that form

my code:

private void add_user_Load(object sender, EventArgs e) 
{ 

      DataSet Ds = new DataSet();

        // Hide   Copy Code
        string strConnectionString = "Data Source=JAMES-PC\\SQLEXPRESS;Initial Catalog=login1;Integrated Security=True";

        SqlConnection objconnection = new SqlConnection(strConnectionString);
        using (SqlCommand cmd = new SqlCommand("SELECT  [username] FROM [user1]",
        objconnection))
        {
            using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
            {
                adapter.Fill(Ds);
            }
        }

        var empList = Ds.Tables[0].AsEnumerable().Select(dataRow =>

        dataRow.Field<int>("username")).ToList();
        comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
        comboBox1.DataSource = empList;

        comboBox1.SelectedIndex = 0;
// Hide   Copy Code
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
   textBox1.Text = comboBox1.SelectedItem.ToString();
}

any help would be much apreciated,thanks in advance

Answer 1

dataRow.Field<int>("username")).ToList();

should be

 dataRow.Field<string>("username")).ToList();

you are casting username to int which should be string.