I'm working on a WPF application and I'm using the MVVM pattern. I use MVVMLight to help me handle some Events. I need to forward the "Click" event so that I can pass the arguments as well so that I can know for sure which item that sent the event. If I use the "Command" I cant know for sure that it was the selected item that sent the event - as the item doesnt need to be selected to right click on it.
This is my code for displaying a list of "order lines". There are two types of order lines, and for one of the data types; "AccessoryOrderLine" - I want to add a context menu.
My problem is that I cannot access my Window's DataContext. I've named the root node in the Window "root", and I'm trying to access the root's DataContext, but this failes with the following error:
System.Windows.Data Error: 4 : Cannot find source for binding with
reference 'ElementName=root'.
BindingExpression:Path=DataContext.PackAccessory; DataItem=null;
target element is 'EventToCommand' (HashCode=5903270); target property
is 'Command' (type 'ICommand')
<ListBox HorizontalContentAlignment="Stretch" Margin="10,0,10,10" DockPanel.Dock="Bottom" Grid.Row="1" ItemsSource="{Binding OrderLines, NotifyOnSourceUpdated=True, NotifyOnTargetUpdated=True, UpdateSourceTrigger=PropertyChanged}">
<ListBox.Resources>
<DataTemplate DataType="{x:Type m:UnitOrderLine}">
<v:OrderLine />
</DataTemplate>
<DataTemplate DataType="{x:Type m:AccessoryOrderLine}">
<v:OrderLine>
<v:OrderLine.ContextMenu>
<ContextMenu>
<MenuItem Header="Pack 1" IsCheckable="False">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<cmd:EventToCommand Command="{Binding ElementName=root, Path=DataContext.PackAccessory }" PassEventArgsToCommand="True" />
</i:EventTrigger>
</i:Interaction.Triggers>
</MenuItem>
</ContextMenu>
</v:OrderLine.ContextMenu>
</v:OrderLine>
</DataTemplate>
</ListBox.Resources>
</ListBox>
I've also tried to use "TemplatedParent" and then I get access to my "OrderLine" DataContext, but I cant get one step further back to my "MainWindowModel".
http://www.thomaslevesque.com/2011/03/21/wpf-how-to-bind-to-data-when-the-datacontext-is-not-inherited/
Found a solution to my problem :)
Found a solution. Updated my original post with the link to my solution.
Its not issue with the DataTemplate. Binding with ElemetName works in all cases except in the case of ContextMenu since it does not lies in the same visual tree as of your window. However, there is one hack where you can use the PlacementTarget property of your context menu.
For details refer to this link - http://social.msdn.microsoft.com/Forums/nl/wpf/thread/526ab350-8788-4bc6-a98a-1e4dee6ad33a
It contains exactly what you are trying to achieve here.
Seems like here are answers for your question:
ElementName Binding from MenuItem in
ContextMenu
WPF MenuItem.Command binding to
ElementName..
Related
I have my hierarchical treeview binding wonderfully to my ViewModel using Caliburn Micro. (The ViewModel has an Items property that returns an ObservableCollection - the treeview is named to this Items property - nothing wrong with the binding).
However the issue comes up with the context menu. The menu fires a method on an instance of the object that the treenode represents. What I rather want to achieve, is to have the menu fire a method on my root ViewModel, passing to it as a parameter the instance of the object represented by the clicked treenode.
Here is my XAML:
<HierarchicalDataTemplate DataType="{x:Type m:TaskGrouping}"
ItemsSource="{Binding Children}">
<Label Content="{Binding Name}"
FontWeight="Bold">
<Label.ContextMenu>
<ContextMenu>
<MenuItem Header="Add New SubFolder"
cal:Message.Attach="AddNewSubfolder" />
<MenuItem Header="Remove this folder"
cal:Message.Attach="RemoveFolder" />
</ContextMenu>
</Label.ContextMenu>
</Label>
</HierarchicalDataTemplate>
What changes do I need to make to my XAML in order to achieve what I want?
ContextMenus are located in a separate visual tree from everything else - it can be a pain to get the bindings right (I often have 10-15 minutes of fighting the bindings on them to get them right!)
You've got your Message.Attach attached property set, all you need to do is ensure that the action target is pointing to the VM rather than the data item. You can use Action.TargetWithoutContext to specify the target for actions (CM will otherwise use DataContext)
You will also need to get a binding path which points to the other visual tree - try using RelativeSource bindings - the ContextMenu also has a property called PlacementTarget which should point to the element that the ContextMenu is attached to
So possibly:
cal:Action.TargetWithoutContext="{Binding DataContext, RelativeSource={RelativeSource AncestorType=Label}}"
or
cal:Action.TargetWithoutContext="{Binding PlacementTarget.DataContext}"
You might have to experiment as I often get this almost right first time!
EDIT by OP(Shawn):
This is what worked for me eventually:
<Label Content="{Binding Name}"
Tag="{Binding DataContext, ElementName=LayoutRoot}">
<Label.ContextMenu>
<ContextMenu
cal:Action.TargetWithoutContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
<MenuItem Header="Run Task Now" cal:Message.Attach="SomeRootViewModelMethod($dataContext)" />
I have a Item control which fills by a list, and list is collection of two parameters 'Time' and 'Description'. For it, i am using a HyperLinkButton for time and a Label for description.
What i want is that, i want to create click event using EventTrigger of hyperLink button in Main viewModel. My code is:
<ItemsControl
x:Name="transcriptionTextControl"
ItemsSource="{Binding MyCollectionOfTranscription, Mode=TwoWay}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<HyperlinkButton Content="{Binding Time}">
<ToolTipService.ToolTip>
<ToolTip Content="Time"/>
</ToolTipService.ToolTip>
<i:Interaction.Triggers>
<i:EventTrigger EventName="Click">
<i:InvokeCommandAction
Command="{Binding HyperLinkButtonCommand}"
CommandParameter="{Binding
ElementName=transcriptionTextControl }" />
</i:EventTrigger>
</i:Interaction.Triggers>
</HyperlinkButton>
<sdk:Label Content="{Binding Description}"/>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
When i build project, it doesn't give error but ICommand for hyperLink, shows warning as 'Cannot resolve symbol HyperLinkButtonCommand', while this event trigger is working fine outside this .
Not getting, what is actual problem behind it, plz give your valuable suggestion...
First off,
<i:InvokeCommandAction
Command="{Binding HyperLinkButtonCommand}"
CommandParameter="{Binding
ElementName=transcriptionTextControl }" />
The Binding is trying to locate a property called HyperLinkButtonCommand on the instance of the type that is contained within MyCollectionOfTranscription (you don't need to bind to this two-way).
(Side note, sending an ItemsControl into your Command is not MVVM.)
The ItemsControl iterates through each element in this collection, creates a copy of the template defined in ItemsControl.ItemTemplate, and sets the BindingContext equal to this element (I assume its a Transcript). You can tell this from the warnings you get from the binding failing to find your HyperLinkButtonCommand if you crank up databinding debug settings.
Assuming
HyperLinkButtonCommand is a command defined in your ViewModel, and
The root of this xaml is a Window (could be a UserControl, but am assuming here)
Your ViewModel is the DataContext of the Window
you can change the binding to the following and it should work (or you should get a clue from it)
<i:InvokeCommandAction
Command="{Binding HyperLinkButtonCommand,
RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}"
CommandParameter="{Binding
ElementName=transcriptionTextControl }" />
I prefer just to give my root an x:Name of "root" and use "ElementName=root" in cases like this.
I'm trying to bind to a property of a container from inside a DataTemplate. A simplified version of my markup looks like:
<Grid>
<Grid.Resources>
<DataTemplate DataType="{x:Type myCustomItem}">
<!--Visual stuff-->
<StackPanel>
<StackPanel.ContextMenu>
<ContextMenu>
<MenuItem Header="Add Item"
Command="{Binding myCustomItemsICommand}"
CommandParameter="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type CustomContainerType}}, Path=ContainerProperty}"/>
</ContextMenu>
</StackPanel.ContextMenu>
</StackPanel>
</DataTemplate>
</Grid.Resources>
<CustomContainerType/>
</Grid>
My approach is based on this post but it doesn't seem to be working. The issue seems to arise from the placement of the ContextMenu within the visual tree. Basically I am trying to bind the Command to the DataContext of the DataTemplate but bind the CommandParameter to a DataContext outside the DataTemplate.
ContextMenus are not in the same visual tree as the rest of the controls, there are a few questions regarding how to do bindings accross that boundary but this might be somewhat difficult without specifying names.
ElementName fails as well because of the lacking tree connection, but you could use x:Reference in the Binding.Source instead.
I have a Treeview in a Silverlight 4 project, and I want to bind to its SelectedItem. When I do a binding to SelectedItem (Mode=TwoWay) its throwing an error in blend because SelectedItem is readonly, which is causing my XAML to not render. I don't ever want to SET the SelectedItem property, I just want to know when it changes via UI interaction. In WPF, I would just bind its SelectedItem using Mode=OneWayToSource, but Silverlight does not support that mode (afaik).
Treeview :
<controls:TreeView ItemsSource="{Binding Repository.MajorClasses}" SelectedItem="{Binding SelectedItem, Mode=TwoWay}" />
Is there a workaround that anyone has used? And anyone know why OneWayToSource is omitted from Silverlight?
It's really readonly, so you cann't do that. You can use TreeView as base control and create CustomTreeView with implementation of bindable SelectedItem. Or create own behavior(attached property). Or use some third party control (f.i. telerik).
If you just want your VM to be informed when the user changes the selection, you should be able to do exactly what you are doing (a two way binding).
I have this working in Visual studio so, I suggest trying it from there, might just be a problem with Blend. VS intellisense doesn't suggest SelectedItem when typing in the XAML editor but that doesn't stop it from working.
The bound property in your VM is definately of the right type (MajorClass by the looks of it)?
What you need to do is make use of an Interaction Trigger and bind it to the SelectedItemChangedevent as follows:
<sdk:TreeView x:Name="ModuleNavigationItemWrappersTreeView" ItemsSource="{Binding ModuleNavigationItemWrappers}">
<sdk:TreeView.ItemTemplate>
<sdk:HierarchicalDataTemplate ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal" Margin="0,2,0,2">
<Image Source="/VanguardFinancials.Common;component/Images/icons/flag_blue.png" />
<TextBlock Margin="2,0,0,0" Text="{Binding ItemDescription}"></TextBlock>
</StackPanel>
</sdk:HierarchicalDataTemplate>
</sdk:TreeView.ItemTemplate>
<interactivity:Interaction.Triggers>
<interactivity:EventTrigger EventName="SelectedItemChanged">
<interactivity:InvokeCommandAction Command="{Binding TrackSelectedModuleNavigationItemWrapper}" CommandParameter="{Binding ElementName=ModuleNavigationItemWrappersTreeView}" />
</interactivity:EventTrigger>
</interactivity:Interaction.Triggers>
</sdk:TreeView>
Visit this for more information about Behaviors and Triggers. Hope this helps.
I have a ListBox that I have added a ContextMenu to. I want one of the items in the ContextMenu to be bound to a command and I want the parameter passed to that command to be the currently selected item of the ListBox control. Here's my xaml:
<ListBox x:Name="selectedVascularBeds"
ItemsSource="{Binding Path=UserSelectedVascularBeds}"
dd:DragDrop.IsDropTarget="True"
dd:DragDrop.DropHandler="{Binding}"
DisplayMemberPath="VascularBedName">
<ListBox.ContextMenu>
<ContextMenu>
<MenuItem Header="Remove" Command="{Binding Path=RemoveSelectedVascularBedCommand}"
CommandParameter="{Binding RelativeSource={RelativeSource
Mode=FindAncestor,
AncestorType={x:Type ListBox}},
Path=SelectedItem}"/>
</ContextMenu>
</ListBox.ContextMenu>
</ListBox>
This ListBox is part of a user control that is bound to a view model object. My command method on the underlying object gets called but the parameter passed in is always null.
I have tested changing the binding of the CommandParameter to simply {Binding} which results in the user control's data context being passed into my method - so I know that the command is working and passes parameters correctly. I just can't seem to get the correct binding to access the ListBox's SelectedItem property.
Help?
the context menu is not a descendant of the list box. try an element name binding instead
<MenuItem Header="Remove" Command="{Binding Path=RemoveSelectedVascularBedCommand}" CommandParameter="{Binding ElementName=selectedVascularBeds, Path=SelectedItem}"/>
The ElementName binding also didn't work, the parameter was still null and I found an error in the console output:
System.Windows.Data Error: 4 : Cannot find source for binding with
reference 'ElementName=selectedVascularBeds'.
BindingExpression:Path=DataContext; DataItem=null; target element is
'MenuItem' (Name=''); target property is 'CommandParameter' (type
'Object')
Searching for that error lead me to this link though and it looks like the Context menu is different and I can't achieve what I want the way I'm going about it.
ElementName Binding from MenuItem in ContextMenu