Adding Enumeration Value to Silverlight Attribute/Property

In the <ImageBrush/> element, there are AlignmentX and AlignmentY attributes with values Left/Center/Right and Top/Center/Bottom, respectively.

What I'm wanting to do is set my own value in, for example, AlignmentX either as a value or as another enumeration like AlignmentX="HalfCenter" where HalfLeft equals my own value (halfway between Center and Left). For example, 开发者_如何转开发if I have this:

    <Rectangle Canvas.Left="0" Stroke="LimeGreen" StrokeThickness="16" Canvas.Top="0" 
               Width="400" Height="400" >
        <Rectangle.Fill>
            <ImageBrush ImageSource="newone.jpg" 
                       Stretch="None" AlignmentX="HalfLeft" AlignmentY="Top"  />
        </Rectangle.Fill>
    </Rectangle>

I don't know if this is a Dependency Property, Attached Property or otherwise (don't yet know how to create those). In the helpfile, it says in TileBrush.AlignmentXProperty field: Public Shared ReadOnly AlignmentXProperty As DependencyProperty. Does the ReadOnly word here mean that I can't set this property to a custom property?

If this can't be an override of that property, how can I create my own? I think this is an Attached Property and it could be called something different, like OffsetX and OffsetY that set an ImageBrush to a location inside its parent Shape. I'm getting very confused by the SL documentation on how I would do this though (almost no examples in VB.NET - but even the C# ones aren't all that revealing).

If it is possible, how would I get started on this?

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Save yourself the pain and just use a value convertor and even that is going to be a little tricky, since you are going to have to apply a rendertransform or something to react to your enums.

You also could write your own panel which is probably a better idea.

You have a few different problems here to confront, creating the attached property, validating the enum, having the enum do what you want it to do when it is set.

Your also going to have to learn about MeasureOverride and ArrangeOverride

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