WPF - The Design view cannot display correctly because some custom elements have not yet been built.

Posted on 2015-02-03
Last Modified: 2015-02-13
Hi Experts,
I've got a working WPF application that has this error from my xaml file.  

I have one warning in the xaml that I think is the cause:
DataType="{x:Type local:MyGroupViewModel}"

The namespace I imported at the top is the following:

MyGroupViewModel most definitely is part of the MyApplication.ViewModels (otherwise the app wouldn't work).  This class has a default constructor, however, it's default constructor does have a base-class initializer like so:
public MyGroupViewModel () : base(null, true) { }

Is the problem potentially the call to base?  What else could I be missing?

Thank you,
Question by:thready
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LVL 96

Expert Comment

by:Bob Learned
ID: 40588784
Does that class have a default constructor?

public MyGroupViewModel()
LVL 25

Expert Comment

ID: 40590104
Syntax wise it looks okie but why u want to pass null,true always. Instead you have avoid this and hard code null and true in your base class.

for testing wise..if you remove the base initialization, is the application working ?

what exactly is your error message ?

Author Comment

ID: 40590264
It does have a default constructor - wouldn't the following be considered a default constructor?
public MyGroupViewModel () : base(null, true) { }

In any case - I removed the need to call the base constructor and now it's just public MyGroupViewModel() {}

The warning I'm getting the the xaml file is:
"The name "MyGroupViewModel" does not exist in the namespace "clr-namespace:MyApplication.ViewModels"

But it does.  Or it wouldn't work right?

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LVL 25

Expert Comment

ID: 40592465
is the view model coming from a referenced dll ? then you need to specify the assembly name.

And hope there is no duplicate class you have.

Author Comment

ID: 40592483
Nope, it's part of the wpf project.  No duplicate class either... :-(

Accepted Solution

thready earned 0 total points
ID: 40597327
I was finally able to fix this by changing

DataType="{x:Type local:MyGroupViewModel}"

to this:

Author Closing Comment

ID: 40607525
This was the only thing that worked for me

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