XamlC Compile errors on a custom control with a list, expected behavior?

So I have a control that has a generic list List. In normal non compiled Xaml I simply use something like:

<controls:CustomControl>
    <controls:CustomControl.FooList>
        <FooBar />
        <FooBar />
        <FooBar />
    </controls:CustomControl.FooList>
</controls:CustomControl>

This works out fine because in the constructor of the cs file I put:

public CustomControl( )
{
    if( FooList == null )
        FooList = new List<FooBar>( );
}

Now you cannot put it in the default of the dependency property because all controls instantiated will use the exact same list(in memory) so I do it in the constructor. Although when using XamlC I get error : Sequence contains no elements because it thinks I am putting in multiple objects into one field instead of a list. Is this expected? If I make a custom list FooBarList : List then it works fine and I have to put two extra lines of code into each xaml file to get around it.

EDIT: This is what works for Xaml using XamlC:

<controls:CustomControl>
    <controls:CustomControl.FooList>
    <controls:FooBarList>
            <FooBar />
            <FooBar />
            <FooBar />
    </controls:FooBarList>
    </controls:CustomControl.FooList>
</controls:CustomControl>

It also sucks having to make custom lists for all my controls that use multiple children, maybe there is a better way?