foreach (DataGridViewRow row in dataGridView1.Rows)
{
if (!row.IsNewRow)
{
if (!Convert.ToBoolean(row.Cells["Column2"].Value)) return;
}
}
foreach (DataGridViewRow row in dataGridView1.Rows)
{
if (!row.IsNewRow)
{
row.Cells["Column2"].Value = false;
}
}