How to check a CheckBox in DataGridview that whether it is checked or not

Question

I have 13 CheckBoxes in a DataGridView in windows form and I want to check all CheckBoxes when the first CheckBox is checked and uncheck all the Checkboxes when the first one is unchecked so how would i do it. my code works for checking all checkboxes but it fails while unchecking. i am using CellContentClick event. here is my code

if (e.ColumnIndex == 1)
            {
                for (int k = 2; k <= 13; k++)
                {
                    DataGridViewCell cell = dataGridView1.Rows[e.RowIndex].Cells[k];
                    DataGridViewCheckBoxCell checkCell = cell as DataGridViewCheckBoxCell;
                    checkCell.Value = true;
                }
            }

Answer 1

Try this:

if (e.ColumnIndex == 1)
{
    DataGridViewCheckBoxCell firstCell =
            dataGridView1.Rows[e.RowIndex].Cells[1] as DataGridViewCheckBoxCell;
    if(firstCell == null)
    {
        return;
    }

    for (int k = 2; k <= 13; k++)
    {
        DataGridViewCell cell = dataGridView1.Rows[e.RowIndex].Cells[k];
        DataGridViewCheckBoxCell checkCell = cell as DataGridViewCheckBoxCell;
        checkCell.Value = firstCell.Value;
    }
}

Answer 2

you assign only true value using for loop you also need to assign false value to checkbox uncheck your all checkbox..

if (e.ColumnIndex == 1)
            {
                for (int k = 2; k <= 13; k++)
                {
                    DataGridViewCell cell = dataGridView1.Rows[e.RowIndex].Cells[k];
                    DataGridViewCheckBoxCell checkCell = cell as DataGridViewCheckBoxCell;
                    checkCell.Value = dataGridView1.Rows[1].Cells[1].Value;
                }
            }