C# enable button when all checkbox in datagridview is clicked

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C#

WinForms

In this program, I want the button is enabled after all the checkbox in datagridview is checked. The current situation is the button will only enabled when the last checkbox in the column is clicked. Any suggestion to solve this problem?

What I have tried:

private void dataGridView2_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
    var senderGrid = (DataGridView)sender;
    senderGrid.EndEdit();
    for (int i = 0; i <= dataGridView2.Rows.Count - 1; i++)
    {
        if (e.RowIndex >= 0)
        {
            var cbxCell = (DataGridViewCheckBoxCell)senderGrid.Rows[i].Cells[1];
            if ((bool)cbxCell.Value)
            {
                btn1.Enabled = true;
            }
            else
            {
                btn1.Enabled = false;
            }
        }
    }

}