private void userDataGrid_BeginningEdit(object sender, DataGridBeginningEditEventArgs e)
{
    if ((string)e.Column.Header == "Initials")
    {
        // If this is the new row, entity is not yet attached to the context.
        if (
            (((User)e.Row.Item).EntityState != EntityState.Detached) &&
            (((User)e.Row.Item).EntityState != EntityState.Added))
        {
            e.Cancel = true;
        }
    }
}

private void gridData_BeginningEdit(object sender, DataGridBeginningEditEventArgs e)
    {
        if ((string)e.Column.Header == "Doctor ID")
        {
            if (!e.Row.IsNewItem)
            {
                e.Cancel = true;
            }
        }
    }