为什么命令绑定到按钮的行为与命令绑定菜单项的行为不同？

Question

Consider the following example with a menu and a button:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
  <DockPanel>
    <Menu DockPanel.Dock="Top">
      <MenuItem Header="Paste" Command="ApplicationCommands.Paste" />
    </Menu>
    <Button Command="ApplicationCommands.Paste">Paste</Button>
    <TextBox>Content</TextBox>
    <TextBox>Content2</TextBox>
  </DockPanel>
</Window>

When I put keyboard focus in one of the text boxes, the TextBox declares that it can handle ApplicationCommands.Paste , and so I expect the button and the menu item to enable themselves. What I get instead is that the menu item enables itself, and the button does not. (The button doesn't appear to be "listening" to the TextBox ' CommandBinding )

What's going on here, and is there any way I can work around this?

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EDIT: I did find this question --> WPF routed command enabling works with menu but not with a button <-- but this is not suitable in this case. The button should not be keyboard focusable, and setting it as a focus scope makes it focusable. I can't bind the source, because the actual source needs to be controlled by keyboard focus.

Answer 1

It appears that you can't use the Command property of a button in this manner unless it's contained in a Toolbar. I get the same results you do with your xaml, but I use the same code regularly to assign this command to a button in a toolbar.

See Copy and paste commands with WPF buttons for more information.

EDIT:

You're right. It has to do with the FocusScope, and there are two ways to fix it, as shown here:

WPF routed command enabling works with menu but not with a button

You can set FocusManager.IsFocusScope on the button:

<Button Command="ApplicationCommands.Paste" FocusManager.IsFocusScope="True">Paste</Button>

Alternately, you can set the button's command target, but this will only work for one textbox.