How to get a MenuItem from within its CanExecute handler?

Question

How can I get access to the related MenuItem? It has been created on the fly, so I cannot just use it by a name in the xaml file.

private void menuItem_canExecute(object sender, CanExecuteRoutedEventArgs e)
{
    var snd = sender; // This is the main window
    var orgSource = e.OriginalSource; // This is a RichTextBox;
    var src = e.Source; // This is a UserControl

    // I think I must use the Command, but how?
    RoutedCommand routedCommand = e.Command as RoutedCommand;
}

You could bind the MenuItem's `CommandParameter` to the MenuItem instance, like `CommandParameter="{Binding RelativeSource={RelativeSource Self}}` and than access it by the `Parameter` property of the CanExecuteRoutedEventArgs. — Clemens, Jan 16 '16 at 15:59
Why do you need access to the `MenuItem`? Maybe there is a better way to accomplish what you are trying to do. — StillLearnin, Jan 16 '16 at 18:19
@Clemens: This is a working solution, please turn your comment into an answer. — Pollitzer, Jan 17 '16 at 08:41
@StillLearnin: In the subitems of a menu "Document" I insert a new item if the user opens a document. After he has closed the document he can easily reopen it by the new menu item. The menu item text consists of a leading number and the document name. To solve the access problem I can use Clemens' proposal. — Pollitzer, Jan 17 '16 at 08:54

StillLearnin · Answer 1 · 2016-01-16T18:12:11.367

1

CanExecuteRoutedEventArgs has an OriginalSource property.

MSDN Doc for CanExecuteRoutedEventArgs

The OriginalSender will probably be a TextBlock which is "inside" the MenuItem. You will likely need to traverse the visual tree to find the parent which is of type MenuItem

Sample code from here

public static T GetVisualParent<T>(this DependencyObject child) where T : Visual
{
    //TODO wrap this in a loop to keep climbing the tree till the correct type is found 
    //or till we reach the end and haven't found the type
    Visual parentObject = VisualTreeHelper.GetParent(child) as Visual;
    if (parentObject == null) return null;
    return parentObject is T ? parentObject as T : GetVisualParent<T>(parentObject);
}

Used like this

var menuItem = e.OriginalSource.GetVisualParent<MenuItem>();
if (menuItem != null)
    //Do something....

edited Jan 16 '16 at 18:12

answered Jan 16 '16 at 15:00

StillLearnin

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If I search the tree for a `MenuItem` I must have at least one unique property which is not there. – Pollitzer Jan 16 '16 at 15:37
Updated my answer to be more clear on what I am suggesting you try. – StillLearnin Jan 16 '16 at 18:12
I tried your proposal, but `e.OriginalSource` in my case is a `RichTextBox` and `GetVisualParent(...)` always returns null. – Pollitzer Jan 17 '16 at 08:40

score 1 · Accepted Answer · answered Jan 17 '16 at 09:23

You can always pass the commanding UI element to a command by binding itself to its CommandParameter property, like

<MenuItem ... CommandParameter="{Binding RelativeSource={RelativeSource Self}}"/>

Now you can access the MenuItem by the Parameter property of the CanExecuteRoutedEventArgs:

private void menuItem_canExecute(object sender, CanExecuteRoutedEventArgs e)
{
    var menuItem = e.Parameter as MenuItem;
    ...
}

How to get a MenuItem from within its CanExecute handler?

2 Answers2