I used this code in window XAML:
<window.inputbindings>
<keybinding command="NotACommand" modifiers="Alt" key="F4" />
<keybinding command="Close" key="F2" />
</window.inputbindings>
<window.commandbindings>
<commandbinding command="Close" executed="CommandBinding_Executed" />
</window.commandbindings>
And this code in the menu:
<menu>
<menuitem header="_File">
<menuitem header="a" />
<separator />
<menuitem header="E_xit" inputgesturetext="F2" command="ApplicationCommands.Close" />
</menuitem>
</menu>
Finally the problem is solved;)