如何选择datagridview中的所有复选框

您好，我已经编写了下面的代码来选择所有复选框，但我无法这样做。请帮助

我尝试过的：

CheckBox HeaderCheckBox=null;
    bool IsHeaderCheckBoxClicked=false;
    private void AddHeaderCheckBox()
    {
        HeaderCheckBox= new CheckBox();
        HeaderCheckBox.Size=new Size(15,15);
        //add check ti DGV
        this.dataGridView1.Controls.Add(HeaderCheckBox);
    }
    private void HeaderCheckBoxClick(CheckBox HCheckBox)
    {
        IsHeaderCheckBoxClicked =true;
        foreach(DataGridView Row in dataGridView1.Rows)
            (DataGridViewCheckBoxCell)Row.CellStateChanged["chk"].value=HCheckBox.Checked;
    }

public void MainFormLoad(object sender, EventArgs e)
		{

AddHeaderCheckBox();
		}

解决方案1

foreach (DataGridViewRow row in dataGridView1.Rows)
{
       DataGridViewCheckBoxCell chk = (DataGridViewCheckBoxCell) row.Cells[0];
       chk.Value = !(chk.Value == null ? false : (bool) chk.Value); //because chk.Value is initialy null
}