Add user name as text & email as value.
while (drd.Read()){
checkedListBox1.Items.Add(new ListItem(drd.GetString(0).ToString(), drd.GetString(1).ToString()));
}
private void checkedListBox1_SelectedIndexChanged(object sender, EventArgs e)
{
string str= String.Empty;
for (int i = 0; i < checkedListBox1.Items.Count; i++)
{
if (checkedListBox1.Items[i].Selected)
{
str = String.IsNullOrEmpty(str)? checkedListBox1.Items[i].Value: str+ ","+ checkedListBox1.Items[i].Value;
}
}
TextBox1.Text = str;
}