AspxGridview with all checkbox column

Answer 1

Set the client instance name on the grid:

ClientInstanceName="YourGrid"

then add a control some where on the page to allow the user to "Select All" like so:

<input id="chkSelectAll" type="checkbox" onclick="YourGrid.SelectAllRowsOnPage(this.checked);" />

Finally in the code behind you can do something like this:

// aColumnName is the name of the column from which you want the value.
private List<object> GetSelectedRowValues(string aColumnName) 
    {
        List<object> values = new List<object>();
        string[] valueToGet = { aColumnName };

        for (int i = 0; i < YourGrid.VisibleRowCount; i++)
        {
            if (YourGrid.Selection.IsRowSelected(i))
            {
                //get the passed in value for the selected rows.
                values.Add(YourGrid.GetRowValues(i, valueToGet));
            }
        }

        return values;
    }