Multipal Selection checkboxes in DataGridView

Question

hi,
i have one datagridview . which is bind from my database (Mysql). i want checkboxes in dgv for multipal select. i got chk boxes in dgv but i dont know why its showing me Error.
here is code for it.
private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
for (int i = 0; i < dataGridView1.Rows.Count;i++)
{
error line//
if
{
((bool)this.dataGridView1.Rows[i].Cells["Select"].Value == true)
{
selectedCheckBox.Add(i);
}
}
}
// this is Error
Object reference not set to an instance of an object.
plz help me .
thanks in Advance

Naeem Khan · Answer

sir still its not working . its showing me but i m not able to check any check box in datagridview.
plz help me sir .......

Roei Bar · Answer

if you cant mark any checkbox it means that the column is markd ReadOnly just goto The DataGrid Properties on the Columns Tab change the ReadOnly Property for that Column to false

Naeem Khan · Answer

thanks for the Reply but they are showing me Check boxes but i cant select even one checkbox. i dont know why . i puted your code but noty working. they are showing me checkboxes but i m not the able to select . i dont know what should i do plz help me
thanks

Roei Bar · Answer

you can use this
foreach (DataGridViewRow dataGridRow in dataGridView1.Rows) {
if (dataGridRow.Cells["checkbox_col"].Value != null &&
( bool )dataGridRow.Cells["checkbox_col"].Value) {
// item is checked
} else if (dataGridRow.Cells["checkbox_col"].Value == null) {
// item is null
}
}