Try code like:
private void gridGroupingControl1_TableControlCurrentCellKeyDown(object sender, GridTableControlKeyEventArgs e)
{
GridCurrentCell cc = e.TableControl.CurrentCell;
if(e.Inner.KeyCode == Keys.F2 && cc.Renderer is GridTextBoxCellRenderer)
{
cc.BeginEdit(true);
TextBoxBase tb = ((GridTextBoxCellRenderer)cc.Renderer).TextBox;
tb.SelectAll();
e.Inner.Handled = true;
}
}