Unable to clear checks from header checkbox in gridview

[Priyam]

I have a gridview which has 1st column as checkboxcolumn. I have a button which clears all checked rows from the grid, below is the code for the same.

foreach (GridViewRowInfo row in gridView.Rows)
{
   row.Cells["bool_helper"].Value = false;
}

But, if all the rows are selected using the header checkbox cell and then the clear button is clicked, the checks from the rows are removed but not from the header check box. I am also not able to set value for the header cell as below. Please suggest.

this.gridView.MasterView.TableHeaderRow.Cells[0].Value = false;