string[] listArr = new string[] { user, name, pass, smsUState, smsContent, tmpAllToMob.ToString(), sender_name };
ListViewItem listLV = new ListViewItem(listArr);
listLV.Tag = Convert.ToInt32(dr["Id"]);
toplist.Items.Add(listLV);

private void button1_Click(object sender, EventArgs e)
{
string myid = toplist.SelectedItems[0].Tag.ToString();
MessageBox.Show(myid);
}

        private void button1_Click(object sender, EventArgs e)
        {
            for (int i = 0; i < 3; i++)
            {
                string[] listArr = new string[] { "user", "name" };
                ListViewItem listLV = new ListViewItem(listArr);
                listLV.Tag = i;
                this.listView1.Items.Add(listLV);
            }

        }

        private void button2_Click(object sender, EventArgs e)
        {
            for (int i = 0; i < this.listView1.SelectedItems.Count; i++)
            {
                string myid = this.listView1.SelectedItems[i].Tag.ToString();
            }
        }