ItemsControl with multiple DataTemplates for a viewmodel

问题

is it possible to bind an itemscontrol with canvas as template to multiple DataTemplates?

I have 2 collections and depending on the type I would like to display a different control on my canvas.

I am not sure but I could think about a Viewmodel which has 2 ObservableCollections. For example if I would have \"Shapes\" and \"connections\" and I would like to display them both on the canvas? In case of a diagraming scenario...

I would like to do this in the mvvm manner and I am not sure if the multiple DataTemplate approach is correct but this came to my mind. But I am still having problems to get the binding straight in my head. If I set the DataContext to the ViewModel for me it seems not possible to bind 2 collections to the items control... =( I am also open for other ideas, too....

Is this possible? And if so, how would the binding look like an

回答1:

You can create multiple ObservableCollections and then bind your ItemsSource to a CompositeCollection which joins those collections.

Then in your XAML you can create different DataTemplates for the respective types using the DataType property which like styles gets automatically applied if it is placed in the resources. (You can also create the composite in XAML which is shown on MSDN, if the CollectionContainers should be bound that is a bit more difficult though)

Example code:

ObservableCollection<Employee> data1 = new ObservableCollection<Employee>(new Employee[]
{
    new Employee("Hans", "Programmer"),
    new Employee("Elister", "Programmer"),
    new Employee("Steve", "GUI Designer"),
    new Employee("Stefan", "GUI Designer"),
    new Employee("Joe", "Coffee Getter"),
    new Employee("Julien", "Programmer"),
});
ObservableCollection<Machine> data2 = new ObservableCollection<Machine>(new Machine[]
{
    new Machine("E12", "GreedCorp"),
    new Machine("E11", "GreedCorp"),
    new Machine("F1-MII", "CommerceComp"),
    new Machine("F2-E5", "CommerceComp")
});
CompositeCollection coll = new CompositeCollection();
coll.Add(new CollectionContainer() { Collection = data1 });
coll.Add(new CollectionContainer() { Collection = data2 });
Data = coll;

<ItemsControl ItemsSource="{Binding Data}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel/>
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.Resources>
        <DataTemplate DataType="{x:Type local:Employee}">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Name}"/>
                <TextBlock Text=" ("/>
                <TextBlock Text="{Binding Occupation}"/>
                <TextBlock Text=")"/>
            </StackPanel>
        </DataTemplate>
        <DataTemplate DataType="{x:Type local:Machine}">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Model}"/>
                <TextBlock Text=" - "/>
                <TextBlock Text="{Binding Manufacturer}"/>
            </StackPanel>
        </DataTemplate>
    </ItemsControl.Resources>
</ItemsControl>

Here i use a different panel but it should be the same for a canvas.

回答2:

You could have ObservableCollection<object> in your ViewModel and bind the ItemsControl's Source to this collection.

Then, to get a different look for different types of data, you could two DataTemplates without x:Key, but with properly set DataType in your Resources. The ItemsControl will then automatically select the appropriate DataTemplate for your item.

回答3:

Have a look at the Data template selector: here or here.

回答4:

Another option with less code behind would be to define two ListBoxes, each with their own templates and bound to their own collections. Define them each in the same physical space and just control which one is visible based on your state. You could even do this with the Visual State Manager and custom states.

来源：https://stackoverflow.com/questions/5473001/itemscontrol-with-multiple-datatemplates-for-a-viewmodel

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wpf

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data-binding

mvvm

viewmodel