C # DataGridView Select all reverse Selection

internal void Addfullselect ()
{
if (This.dtGrdVwMdt.Rows.Count < 1)
{
Return
}
System.Windows.Forms.CheckBox Ckbox = new System.Windows.Forms.CheckBox ();
Ckbox.text = "Select All";
ckbox.checked = false;
System.Drawing.Rectangle rect =
This.dtGrdVwMdt.GetCellDisplayRectangle (0,-1, true);
Ckbox.size = new System.Drawing.Size (This.dtgrdvwmdt.columns[0]. Width, 25);
Ckbox.location = rect. Location;
Ckbox.checkedchanged + = new EventHandler (ckbox_checkedchanged);
THIS.DTGRDVWMDT.CONTROLS.ADD (Ckbox);
}
internal void Ckbox_checkedchanged (object sender, EventArgs e)
{
for (int i = 0; i < This.dtGrdVwMdt.Rows.Count; i++)
{
This.dtgrdvwmdt.rows[i]. Cells[0]. Value = ((System.Windows.Forms.CheckBox) sender). Checked;
}
This.dtGrdVwMdt.EndEdit ();
}

Determine if checkbox is selected

1. for (int i = 0; i < DataGridView1.Rows.Count; i++)
2. {
3. if ((bool) datagridview1.rows[i]. Cells[0]. editedformattedvalue==True)
4. {
5. //todo
6. }
7. }

C # DataGridView Select all reverse Selection