WINRT XAML System.Void Compile Error in

Question

after a little code change inside a Store App I ran into a compilation error:

-> System.Void cannot be used from C# -- use typeof(void) to get the void type object.

Problem is: this comes from a generated file: XamlTypeInfo.g.cs.

case "System.Void"
    userType= new ... ,typeof(global::System.Void), ...
    ...

Rolling back the changes did not help, as deleting bin & obj, restarting, etc.

Is the actual System.Void case entry maybe an indicator that something within a XAML file could not be recognized by the code generator? Is there an System.Void entry in a working XamlTypeInfo.g.cs?

--- ADDITION --- I can now produce the compile error when changing specific lines. I have a custom control deriving from ItemsControl. I define a regular DP which works fine. I am also providing AttachedProperties for Template, TemplateSelector and Style. Think of a Textbox that gets an Label via an AttachedProperty and its not just a string but like HeaderedControls you can define a Template etc. for the Lable.

The Problem is related to the Get/Set Methods for the AttachedProp. When I either change the Getter return type to DataTemplate or I comment out the Setter fully then the compile error comes:

public static DataTemplate GetLabelTEmplate(UIElement element)
{
    return (DataTemplate)element.GetValue(LabelTemplateProperty;
}

public static void SetLabelTemplate(UIElement element, object value)
{
    element.SetValue(LabelTemplateProperty, value);
}

Any ideas would be highly appreciated.

Best regards Gope

Can you post the XAML associated with this attached property? — Paul Michaels, Feb 20 '13 at 16:56
There is no XAML using the properties yet. Just the control and it doesn't compile. Interesting though a colleague used the same project from another branch to manually add those APs and it compiles. XamlTypeInfo is generated correctly. I will try creating a new project and move things over, just to see if it works. — Gope, Feb 21 '13 at 07:42
I just filed a bug report with an attachment at connect.microsoft: https://connect.microsoft.com/VisualStudio/feedback/details/779775/windows-8-store-apps-attachedproperties-of-referencetypes-results-in-compile-error-system-void Let's see what they think about it. — Gope, Feb 22 '13 at 09:17

score 0 · Accepted Answer · answered Mar 04 '13 at 09:26

0

After filing a bug complaint with microsoft they pointed me to the problem: The setter's value cannot be of type object. This information is needed for the XamlTypeInfo generation so when I changed object to DataTemplate it compiled.

Although I haven't tried it yet, I believe object is fine for plain WPF, but for Win 8 Store apps this does result in an compilation Error. Funny stuff... :)

answered Mar 04 '13 at 09:26

Gope

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I had hoped your solution could have helped, but unfortunately I keep getting the same error even though my setter’s value isn’t of type object but MediaCapture, as I am trying to bind it to a CaptureElement. – Frederik Krautwald May 28 '14 at 14:18
Show me your CLR Property – Gope May 28 '14 at 14:21
`public static MediaCapture GetMediaCaptureSource(DependencyObject captureElement) { return captureElement.GetValue(MediaCaptureSourceProperty) as MediaCapture; }` `public static void SetMediaCaptureSource(CaptureElement captureElement, MediaCapture mediaCapture) { captureElement.SetValue(MediaCaptureSourceProperty, mediaCapture); }` – Frederik Krautwald May 28 '14 at 14:33
1

Hmmm... only difference to the usual samples I can see is in the Setter the first parameter which is of type CaptureElement. My definitions are usually UIElement or in your case it could be DependencyObject. You probably did that to only allow setting the Property at Capture elements but I am unsure if that might be the problem. Can't check though right now. Maybe just change it into DependencyObject for a quick test. – Gope May 28 '14 at 14:43
it appears that at least in WPF that's not possible... http://stackoverflow.com/questions/6874427/limit-attached-dependency-property-in-wpf – Gope May 28 '14 at 14:44
That solved it. Thank you. A fresh pair of eyes are always good. – Frederik Krautwald May 28 '14 at 14:46

WINRT XAML System.Void Compile Error in

1 Answers1