I made a Silverlight project like this:
<UserControl x:Class="silverlighttest3.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" Height="270" Width="487">
<Grid x:Name="LayoutRoot" Background="blue" Height="270" Width="487" HorizontalAlignment="Stretch">
<MultiScaleImage HorizontalAlignment="Left" Margin="146,27,0,0" Name="multiScaleImage1" VerticalAlignment="Top" Source="Source/dzc_output.xml"/>
</Grid>
and after that I tested it and it worked just fine.
The problem is when testing the web Application that hosted the Silverlight project, when trying the ‘testsilverlight.aspx’ there is nothing shown.
Note: the source folder is in the Silverlight directory and not in the web application directory. and when copied it to web application directory the result is same – a white page.
I found a link that might help you: Source attribute of Silverlight MultiScaleImage
Also, I’m not sure how your project structure is set up but make sure that the build action on your xml file is set to Content and that its being included inside your xap file after its built in the same relative folder structure.