Question

i have a some questions about WPF + MVVM + ElementHost. I try to explain it so clear i can.

1. I’m building an addin(VSTO 2010) that’s mean i need an ElementHost to hosted a WPF.

2. The first Point mean that my WPF can only be an UserControl (WPF)

3. Regarding Point 1 and 2 ;

   It’s possible to build an MVVM WPF(UserControl) having Popup(Children) like this One and which can be hosted into a ElementHost?

I hope my Question is enough clear! Thank u for helping.

Answer 1

You sure can, there are a few gotcha’s though.

I have had issues with my WPF control not drawing when initially displayed, so I worked around it by tweaking the width when the Child is set. See http://vstocontrib.codeplex.com/SourceControl/changeset/view/50a83624e34d#src%2fVSTOContrib.Core%2fWpf%2fWpfPanelHost.cs

Next is the MVVM style application you want to build, the main issue around this is the VSTO model around windows/documents/custom task panes are all different, one is based on the open workbook (context), one is windows (view) and custom task panes are also window based (view).
MVVM style apps are built more around the current context, or the current opened workbook, I have been working on VSTO contrib for a while now to solve this problem, it even gives you MVVM like bindings when declaring your RibbonXML ribbons if you need ribbon support.
Grab it at http://vstocontrib.codeplex.com and please let me know if it indeed helps you.

And finally the popup, there is nothing stopping you, but you will find in Office 2007 that when you try to open the window for a second time that Office will probably crash. The following code will make your WPF window experience a bit smoother.

if (System.Windows.Application.Current == null)
    new Application { ShutdownMode = ShutdownMode.OnExplicitShutdown };
else
    System.Windows.Application.Current.ShutdownMode = ShutdownMode.OnExplicitShutdown;

Basically when you display the first window, all is good, but WPF will spin up a Application, which by default exits when the last window is closed. So when your window closes, then you try to open it again, WPF will blow up 😛