I have the following setup:
<ListBox ItemSource="{Binding Targets}">
<ListBox.ItemTemplate>
<DataTemplate>
<view:ViewName />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
What I am trying to accomplish is to dynamically decide which view to use at runtime, based on a property within the DataContext of the ListBox. In simple terms, I want to replace <view:ViewName> with a data binding that returns the proper view.
I use MEF to provide plug-ins for my app that may need to provide a custom view to display the items when appropriate. At design time I won't know all the possible view types (they may be dynamically loaded from a DLL) so a simple DataTemplateSelector won't do.
I have researched solutions but have come up empty.
Since you want to change templates based on a bound value, you can use a DataTrigger to determine the ContentTemplate of the ListBoxItem
<Style TargetType="{x:Type ListBoxItem}">
<Setter Property="ContentTemplate" Value="{StaticResource DefaultTemplate}"/>
<Style.Triggers>
<DataTrigger Property="{Binding SomeProperty}" Value="A">
<Setter Property="ContentTemplate" Value="{StaticResource TemplateA}"/>
</DataTrigger>
</Style.Triggers>
</Style>
I find this better than using a DataTemplateSelector because it gets re-evaluated if the bound property changes, while a DataTemplateSelector does not.
If you want to change templates based on an object type, you can use Implicit DataTemplates. These are DataTemplates that define a DataType, but no x:Key, and they will be used anytime WPF tries to draw an object of the specified type.
For example, if you had this template defined in your <X.Resources> somewhere
<DataTemplate DataType="{x:Type models:ActionA}">
<views:ActionAView />
</DataTemplate>
you could then insert your Model object directly into the UI and WPF would draw it using the template you specified
<ContentControl Content="{Binding SomeIActionObject}" />
<ItemsControl ItemsSource="{Binding CollectionOfIActionObjects}" />
Update
You mentioned that you would be allowing users to create modules with additional Templates that get imported using MEF, so in that case you would probably be better off using an IValueConverter that look up the matching template within Application.Resources
For example, if the bound value equals "A", then the converter might search Application.Resources for a template named "TemplateA" and return it to the binding
<Style TargetType="{x:Type ListBoxItem}">
<Setter Property="ContentTemplate"
Value="{Binding SomeProperty,
Converter={StaticResource MyTemplateConverter}}"/>
</Style>
Using the DataTemplateManager from this post You can do something like:
DataTemplateManager.RegisterDataTemplate<ViewModelType1, ViewType1>();
DataTemplateManager.RegisterDataTemplate<ViewModelType2, ViewType2>();
DataTemplateManager.RegisterDataTemplate<ViewModelType3, ViewType3>();
then you would remove the ItemTemplate from the ListBox:
<ListBox ItemSource="{Binding Targets}"/>
and in the ListBox ViewModel you could:
public void AddTargets()
{
Targets.Add(new ViewModelType1());
Targets.Add(new ViewModelType2());
Targets.Add(new ViewModelType3());
}
Then, each DataTemplate will be automatically used by WPF to render each corresponding ViewModel.
Also note that you can call DataTemplateManager.RegisterDataTemplate() at any time before showing the ListBox, so you can theoretically do that when loading the MEF parts.
Edit:
Based on your comment, you could create a single DataTemplate with a ContentPresenter to display the selected View according to a property in the ViewModel:
<DataTemplate DataType="{x:Type local:TargetViewModel}">
<ContentPresenter x:Name="MainContentPresenter" Content="{Binding}" ContentTemplate="{Binding YourProperty, Converter=SomeConverter}"/>
and inside the SomeConverter you should use the same technique as demonstrated in the post, to dynamically generate a DataTemplate.
Related
I'm customizing a WPF DataGridCell style, but once I've done this double click to edit no longer works. I've also tried to manually call myDataGrid.BeginEdit, but nothing seems to happen. This is code similar to what I have:
<Style x:Key="MyCell" TargetType="{x:Type DataGridCell}" BasedOn="{StaticResource {x:Type DataGridCell}}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Border>
<TextBlock />
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I assume the problem is that because I'm overriding the ControlTemplate, an editor no longer exists? If that's the case, is their a way I can sort this to use the default editor?
I'm using a subclassed TextBlock which sets different foreground colours for individual words in the content string. I couldn't figure out how to do that without replacing the ControlTemplate.
Instead of creating a custom ControlTemplate , you should create a custom column type and override the GenerateElement method to return an instance of your custom type:
public class CustomColumn : DataGridTextColumn
{
protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
{
return new YourCustomTextBlock();
}
}
Generally, you should avoid overriding ControlTemplates unless you really need to make substantial changes to the functionality or layout of a control (or if your building your own). You can usually do what you need with DataTemplates instead, which keep the underlying control intact, but customize the way your data is displayed.
For the DataGrid, there is a special type of column type meant just for this: DataGridTemplateColumn. Here's a quick example of how to use it:
<DataGrid>
<DataGrid.Columns>
<DataGridTemplateColumn>
<DataGridTemplateColumn.CellTemplate>
<!--This is used when the cell is being displayed normally-->
<DataTemplate>
<TextBlock Text="{Binding SomePropertyOfYourRow}"/>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
<DataGridTemplateColumn.CellEditingTemplate>
<!--This is used when the cell is being edited (e.g. after double-click)-->
<DataTemplate>
<TextBox Text="{Binding SomePropertyOfYourRow}"/>
</DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
You can easily put your custom TextBlock into the CellTemplate and it will be use to display the contents of that cell.
I bind list of objects to my ListBox in WindowsPhone application. This business object has one boolean property. Based on the Boolean property i need to set the IsEnabled property in the ListBoxItem.
Is there any way to achieve this in WindowsPhone ListBox ?
There're few ways to achieve this:
You can add the ListBoxItem by C# code and set the property properly.
In Xaml, inside the list box, place the following:
<ListBox.Resources>
<Style TargetType="ListBoxItem">
<Setter Property="IsEnabled" Value="{Binding Content.IsEnabled, RelativeSource={RelativeSource Self}}"/>
</Style>
</ListBox.Resources>
Here I assume that the property name in your model object is IsEnabled, change it according to its real name.
I have an object MyResult that contains a list "List MyItems".
I would like to add this to a c# WPF TreeView.
What would be the best way to do so?
Is there a step-by-step tutorial for this? Since I'm getting confused with all the MVVM Classes etc.
Thanks
I'm assuming your objects in your list have some sort of list.
if thats the caseyou should look at using the hierarchicaldatatemplate.
a simple example might be something like the following. This is from a segment I used with a radtreeview but it should work the same.
<!-- xaml -->
<UserControl.Resources>
<Style x:Key="_treeViewItemStyle" TargetType="telerik:RadTreeViewItem">
<Setter Property="Visibility" Value="{Binding IsVisible, Converter={StaticResource VisibilityConverter}}" />
<Setter Property="IsEnabled" Value="{Binding IsEnabled}"/>
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
<Setter Property="HorizontalAlignment" Value="Left"/>
</Style>
<UI:HierarchicalDataTemplate x:Key="_treeViewTemplate"
ItemsSource="{Binding NodeItems}"
>
<TextBlock Margin="3,0,0,0" Text="{Binding Header}">
</TextBlock>
</UI:HierarchicalDataTemplate>
</UserControl.Resources>
<telerik:RadTreeView x:Name="_pageNavigator" ItemsSource="{Binding InspNavList}" ItemDoubleClick="SendFocusToPage" SelectedItem="{Binding SelectedNavItem, Mode=TwoWay}" ItemTemplate="{StaticResource _treeViewTemplate}" ItemContainerStyle="{StaticResource _treeViewItemStyle}" />
You can use
treeview.ItemsSource = MyList.
Here is a tutorial how to do it using MVVM.
There's no best way to do things. Well, actually there is, but you need a bit more data about the system itself and the current situation (as well as some profound knowledge) to know the best way to do things. Well, putting that aside.
If you'd like to use binding, you could do the following:
a. In your page/window/usercontrol set DataContext property to point to your object (MyResult).
b. In your XAML file use following snippet to bind treeView items to that list:
<TreeView ItemsSource={Binding MyItems}>
....
</TreeView>
c. Enjoy the result.
There are several things you need to consider, though:
1. You should implement DataTemplate for your MyItems objects. Default implementation would just take ToString() result to put into the tree view.
2. If you'd like to use hierarchical data (meaning the one that has levels), you should implement HierarchicalDataTemplate and point where to get children for every node in the tree.
3. You should consider using ObservableCollection for correct binding - this way every addition/deletion of an item in the list would invoke changes in the UI.
Here are several links to get you started: first, second, third.
I would like to avoid having to build a menu manually in XAML or code, by binding to a list of ICommand-derived objects. However, I'm experiencing a bit of a problem where the resulting menu has two levels of menu-items (i.e. each MenuItem is contained in a MenuItem):
My guess is that this is happening because WPF is automatically generating a MenuItem for my binding, but the "viewer" I'm using actually already is a MenuItem (it's derived from MenuItem):
<ContextMenu
x:Name="selectionContextMenu"
ItemsSource="{Binding Source={x:Static OrangeNote:Note.MultiCommands}}"
ItemContainerStyleSelector="{StaticResource separatorStyleSelector}">
<ContextMenu.ItemTemplate>
<DataTemplate>
<Viewers:NoteCommandMenuItemViewer
CommandParameter="{Binding Source={x:Static OrangeNote:App.Screen}, Path=SelectedNotes}" />
</DataTemplate>
</ContextMenu.ItemTemplate>
</ContextMenu>
(The ItemContainerStyleSelector is from http://bea.stollnitz.com/blog/?p=23, which allows me to have Separator elements inside my bound source.)
So, the menu is bound to a collection of ICommands, and each item's CommandParameter is set to the same global target (which happens to be a collection, but that's not important).
My question is, is there any way I can bind this such that WPF doesn't automatically wrap each item in a MenuItem?
Unfortunately, the best way I've found to work around this issue is to use a style for the MenuItems, rather than an ItemTemplate. Then each property in the style can be bound to properties on your object. Something like this, for example:
<Style x:Key="SelectionContextMenuStyle" TargetType="MenuItem">
<Setter Property="Header" Value="{Binding Path=Text}" />
<Setter Property="Command" Value="{Binding Path=Command}" />
<Setter Property="CommandParameter" Value="{Binding Path=Parameter}" />
</Style>
It really seems like an ItemTemplate should work, and it would be the better way to go, but this is the only way I've found that actually works properly.
I would be inclined to subclass ContextMenu and override GetContainerForItemOverride:
public class ContextMenuWithNoteCommands : ContextMenu
{
protected virtual DependencyObject GetContainerForItemOverride()
{
return new NoteCommandMenuItemViewer();
}
}
Then set the CommandParameter binding in the NoteCommandMenuItemViewer style, or in ContextMenu.ItemContainerStyle, whichever is more appropriate.
This presumes you can't simply use ItemContainerStyle on a regular MenuItem to get the effect you want:
<ContextMenu ...>
<ContextMenu.ItemContainerStyle>
<Style>
...
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
I have a list of objects. For each item in the list, I want to create a new user control bound to that item. From what I've read, doing this programmatically is bad practice with WPF (as well as less than straightforward), so I should use data binding as a solution instead. The problem is, I can't figure out how to do this. I don't know the contents of the list (just the type) at compile-time, so I can't create and bind with XAML for each element. Google and MSDN don't seem to have any answers, so maybe I'm thinking about this the wrong way? What do I need to do?
Thanks
EDIT: To clarify, I'm trying to make my own music scoring software, something like Rosegarden. The list would contain all of the measures, and the usercontrols would be their visual representation.
A more generic approach than Julien Lebosquain's suggestion (and one that will work when the list of items contains objects of more than one data type):
Create a DataTemplate to be used in presenting an item of the type(s) in your list, e.g.:
<DataTemplate DataType="local:Measure">
<local:MeasureUserControl DataContext="{Binding}"/>
</DataTemplate>
Use an ItemsControl to present the items:
<ItemsControl ItemsSource="{Binding MeasureList}"/>
You can set the ItemsPanel property of the ItemsControl to an ItemsPanelTemplate to govern how it will lay out the user controls, e.g.:
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
This approach is generally preferable to using a ListBox when you don't want the features of the ListBox, e.g. its default border and selection behavior.
You can use a standard ListBox with a custom item style:
Somewhere in the resources:
<Style TargetType="{x:Type ListBoxItem}" x:Key="CustomItemStyle">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBoxItem}">
<yourns:YourControl />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
In your window/page/usercontrol:
<ListBox ItemsSource="{Binding ...}" ItemContainerStyle="{StaticResource CustomItemStyle}" />
Since your objects will be bound to the listbox, an implicit ListBoxItem will be created for each object, with its DataContext set to the object so you can use bindings in YourControl without any worries.
All the above answers work, but I'll leave with how I'm doing this in my application.
I'm implementing the MVVM architecture that takes advantage of these WPF features.
This is a UserControl I'm using that has an ItemsControl populated with the items of a certain type:
<UserControl x:Class="Controls.StepView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:my="clr-namespace:Controls"
Background="Transparent">
<UserControl.Resources>
<DataTemplate DataType="{x:Type my:ParameterViewModel}" >
<my:ParameterView HorizontalAlignment="Stretch" Margin="25 0 0 0"/>
</DataTemplate>
</UserControl.Resources>
<Grid>
<ItemsControl Name="stkStepContent" ItemsSource="{Binding Parameters}" />
</Grid>
</UserControl>
Let me explain the code for you. in the DataTemplate section I say that I want to render objects of class ParameterViewModel with the UserControl ParameterView. The ItemsSource property of my ItemsControl is binded to a List<ParameterViewModel>. When the ItemsControl is initiated for each ParameterViewModel on the List it will create a ParameterView and set its DataContext to the ParameterViewmodel it is rendering.
I found that this architectural pattern is the most intuitive for me to build WPF applications.