CommandParameters in ContextMenu in WPF

Question

I have a scenario where I have a WPF TreeView control that has an HierarchicalDataTemplate for its items. Now inside the HierarchicalDataTemplate, I have a Label and the Label has a ContextMenu with a menuitem for Delete. The Delete menuitem is bound to a Command called DeleteCommand which is a part of the class that has been set as the DataType of the HierarchicalDataTemplate.

Now, I want to pass the TreeView control in the CommandParameters of the ContextMenu's Delete menuitem's DeleteCommand so that I can handle the selection of the TreeViewItems on the deletion of the currently selected item.

But if I bind the CommandParameters as the {Binding ElementName=TreeViewName} or whatever for that matter, it is always null unless the binded element is a property in the DataContext.

Can anyone help me with a solution because I think, I have tried all the possible things such as RelativeSource and AncestorType etc but its always null. To me, it looks like either a limitation or a bug in the framework.

score 20 · Answer 1 · edited Feb 29 '12 at 23:49

The problem is that the ContextMenu is at the root of its own visual tree, so any RelativeSource.FindAncestor bindings won't go past the ContextMenu.

One solution is to use the PlacementTarget property to set up a two-stage binding from your Label:

<Label Tag="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={
    x:Type TreeView}}}">
    <Label.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Delete" Command="{x:Static local:Commands.DeleteCommand}"
                CommandParameter="{Binding PlacementTarget.Tag, RelativeSource={
                RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}}"/>
        </ContextMenu>
    </Label.ContextMenu>
</Label>

This is quite hacky, however. You're better off setting the CommandTarget property of your MenuItem to the ContextMenu's PlacementTarget and having the command handler on your TreeView. This means you won't have to pass the TreeView around.

@JoanComas: after trying all the others without success (nor understanding what it all meant with FindAncestors, etc), your Way easy way works perfectly! Thanks. — joedotnot, May 09 '13 at 07:48
@JoanComasFdz 's comment is really help. I can apply `CommandParameter="{Binding}"` simply. — Youngjae, Nov 10 '15 at 04:55

score 1 · Answer 2 · answered Aug 12 '15 at 14:34

<ContextMenu>
    <MenuItem Header="Edit Item"
                   Command="{Binding EditItemCommand, Mode=OneWay}"
                   CommandParameter="{Binding Path=UIElement.(views:DataGridView.SelectedItems), RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}" />
<ContextMenu>

score 0 · Answer 3 · edited Feb 03 '17 at 20:11

0

<MenuItem Header="..." 
          Command="{Binding Path=...}" 
          CommandParameter="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Mode=FindAncestor, AncestorLevel=1, AncestorType={x:Type ContextMenu}}}">
</MenuItem>

ContextMenu.PlacementTarget, is Label, where the menuitem is hosted. From Lavel, its parent Treeview is accessable.

edited Feb 03 '17 at 20:11

ΩmegaMan

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answered May 16 '13 at 03:56

user714307

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score 0 · Answer 4 · edited May 23 '17 at 11:54

0

Take a look at WPF CommandParameter Binding Problem. Maybe it can provide some pointers as to what's going on.

edited May 23 '17 at 11:54

Community

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answered Feb 02 '09 at 19:36

Szymon Rozga

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score 0 · Answer 5 · answered Jan 06 '21 at 16:56

For each element in DataGrid

<ContextMenu>
    <MenuItem Header="Edit Item"
                   Command="{Binding EditItemCommand, Mode=OneWay}"
                   CommandParameter="{Binding Path=PlacementTarget.SelectedItem, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}" />
<ContextMenu>

CommandParameters in ContextMenu in WPF

5 Answers5

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