WPF - Referencing multiple resources

Experts,

开发者_C百科

In XAML I would like to create a many-to-many relationship between entities.

Basically I would like for multiple "Manager" objects to be able to manage multiple "Items". The following XAML should describe what I'm looking for:

<Grid>
    <Grid.Resources>
        <cc:Manager x:Key="Manager1"/>
        <cc:Manager x:Key="Manager2"/>
    </Grid.Resources>
    <cc:Item>
        <cc.Manager.ManagedBy>
            <StaticResource ResourceKey="Manager1" />
        </cc.Manager.ManagedBy>
    </cc:Item>
    <cc:Item>
        <cc.Manager.ManagedBy>
            <StaticResource ResourceKey="Manager1" />
            <StaticResource ResourceKey="Manager2" /> <!-- ERROR HERE -->
        </cc.Manager.ManagedBy>
    </cc:Item>
    <cc:Item>
        <cc.Manager.ManagedBy>
            <StaticResource ResourceKey="Manager2" />
        </cc.Manager.ManagedBy>
    </cc:Item>
</Grid>

The attached property (Manager.ManagedBy) is of type ManagedByCollection...

ManagedByCollection : List<ManageBy>

With this I get the following error message:

The object 'Object' already has a child and cannot add 'StaticResourceExtension'. 'Object' can accept only one child. Line NN Position NN.

So, I wen't back to MSDN and realized there's a ContentPropertyAttribute to tell the XAML compiler what property is the default one when nothing else is specified. The LinearGradientBrush, for example, uses that attribute to enable us to write just ...

<LinearGradientBrush ... >
   <GradientStop ... />
   <GradientStop ... />
   <GradientStop ... />
</LinearGradientBrush>

... instead of ...

<LinearGradientBrush ... >
   <GradientStopCollection>
       <GradientStop ... />
       <GradientStop ... />
       <GradientStop ... />
   </GradientStopCollection>
</LinearGradientBrush>

So, I was thinking I just needed to specify the indexer of ManagedByCollection as the class' ContentProperty:

[ContentProperty("Item")
ManagerCollection : List<Manager>

Unfortunately, this does not resolve the issue. Currently the following works...

<cc.Manager.ManagedBy>
    <ManagerCollection>
        <StaticResource ResourceKey="Manager1" />
        <StaticResource ResourceKey="Manager2" />
    <cc:ManagerCollection>
</cc.Manager.ManagedBy>

... but, again, I would prefer the more readble syntax:

<cc.Manager.ManagedBy>
    <StaticResource ResourceKey="Manager1" />
    <StaticResource ResourceKey="Manager2" />
</cc.Manager.ManagedBy>

Any help or hints would be appreciated.

---

You can initialize the collection explicitly in the constructor of Item:

public Item()
{
    Manager.SetManagedBy(this, new ManagedByCollection());
}