Checkbox Disabled in GridView

foreach (GridViewRow gr in gridView1.Rows)
{
    string errType = gridView1.DataKeys[rowIndex].Values["Err"].ToString()
    if (errType != null && errType != "")
    {
        CheckBox cb = (CheckBox)gr.Cells[0].FindControl("chkError");
        cb.Enabled = true;
        cb.Checked = true;
    }
    else
    {
        CheckBox cb = (CheckBox)gr.Cells[0].FindControl("chkError");
        cb.Enabled = false;                        
    }
}