I have a `List<Car>` objects that have a `bool` property named **`Marked`**.  

I want to **check / uncheck** the Cell corresponding to this property, in a way that **only one** `Car` can be selected at the **same time**.  

I want that the value of this property is updated in the bank.

Sample table:

| Car Name | Marked |
| --- | --- |
| a |  |
| b |  |

The problem is I can't check the state of CheckBox Cells.  

This is what I tried, but it's not working:

**Example 1:**

```
DataGridViewCheckBoxCell dataGridViewCheckBoxCell = DataGridView1.Rows[e.RowIndex].Cells["Marked"] as DataGridViewCheckBoxCell;

if(Convert.ToBoolean(dataGridViewCheckBoxCell.Value) == true)
{
        //some code
}
else if(Convert.ToBoolean(dataGridViewCheckBoxCell.Value) == false)
{
        //some code
}

```

**Example 2:**

```
foreach (DataGridViewRow row in DataGridView1.Rows)
{
    DataGridViewCheckBoxCell chk =(DataGridViewCheckBoxCell)row.Cells["Marked"];

    if (chk.Value == chk.TrueValue)
    {
        chk.Value = chk.FalseValue;
    }
    else
    {
        chk.Value = chk.TrueValue;
    }
}

```

how can I do it?