Use the listView1_ItemCheck() event of the ListView control and write the following code.
Now you can find easily which checkbox is checked which is not.
private void listView1_ItemCheck(object sender, ItemCheckEventArgs e)
{
ListViewItem l = listView1.Items[e.Index];
if (e.NewValue == CheckState.Checked)
{
MessageBox.Show(l.ToString() + " is checked.");
}
else
{
MessageBox.Show(l.ToString() + " is UNchecked.");
}
}