Problem with generating XPS documents with images in a WCF class library

Question

I have a Silverlight application which uses a web service in order to create XPS documents. The document templates are created as XAML controls in a WCF class library.

public void GenerateXPS()
{
    Type typeofControl = Type.GetType(DOCUMENT_GENERATOR_NAMESPACE + "." + ControlTypeName, true);
    FrameworkElement control = (FrameworkElement)(Activator.CreateInstance(typeofControl));

    control.DataContext = DataContext;

    FixedDocument fixedDoc = new FixedDocument();
    PageContent pageContent = new PageContent();
    FixedPage fixedPage = new FixedPage();

    //Create first page of document
    fixedPage.Children.Add(control);
    ((IAddChild)pageContent).AddChild(fixedPage);
    fixedDoc.Pages.Add(pageContent);
    XpsDocument xpsd = new XpsDocument(OutputFilePath + "\\" + OutputFileName, FileAccess.ReadWrite);
    System.Windows.Xps.XpsDocumentWriter xw = XpsDocument.CreateXpsDocumentWriter(xpsd);
    xw.Write(fixedDoc);
    xpsd.Close();

    SaveToDocumentRepository();
}

In order to bind the actual data to my document template I set the DataContext property of the control. The problem is that when I look at my XPS, the images (I bind the Source of my Image controls to a string property that represents the URL of my image) are not displayed as if they were not loaded. How can I solve this problem? Thanks!

Answer 1

The binding infrastructure probably needs a push along because you are operating outside the intended use of WPF.

Try adding the following code after setting the datacontext:

control.DataContext = DataContext;

// we need to give the binding infrastructure a push as we
// are operating outside of the intended use of WPF
var dispatcher = Dispatcher.CurrentDispatcher;
dispatcher.Invoke(
   DispatcherPriority.SystemIdle,
   new DispatcherOperationCallback(delegate { return null; }),
   null);

I cover this and other XPS related stuff in this blog post.