CommunityToolkit.Mvvm Not Exposing Any Methods

Question

CommunityToolkit.Mvvm Not Exposing Any Methods

RogerSchlueter-7899 1,446

I have addded the CommunityToolkit.Mvvm (Version 8.1.0 to my project via NuGet. It is a wpf, .NET 6.0 project. Here are the relevant parts of my MainWindow ViewModel:

Imports CommunityToolkit.Mvvm.Input
Imports System.Data
Imports System.Data.SqlClient
Imports System.IO

Public Class MainWindowVM
    Inherits ObservableObject
    Implements IDisposable
    ....
    Private _SelectedValue As String
    Public Property SelectedValue As String
        Get
            Return _SelectedValue
        End Get
        Set(value As String)
            SetProperty(_SelectedValue, value)
        End Set
    End Property
    ....
End Class

The SetProperty method gives compile-time error: 'SetProperty' is not declared. It may be inaccessible due to its protection level. I have tried other methods that are supposed to be available but none are recognized. What is missing?

Hui Liu-MSFT 48,676 Microsoft External Staff

Hi,@Roger Schlueter. I use the following code, right -click the project for rebuild, and the error disappears. Did I miss something? If you have any questions, please provide more details.

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Imports CommunityToolkit.Mvvm.ComponentModel
Imports CommunityToolkit.Mvvm.Input
Imports System.Data
Imports System.Data.SqlClient
Imports System.IO

Public Class MainWindowVM
    Inherits ObservableObject
    Implements IDisposable

    Private _SelectedValue As String
    Public Property SelectedValue As String
        Get
            Return _SelectedValue
        End Get
        Set(value As String)
            SetProperty(_SelectedValue, value)
        End Set
    End Property

    Public Sub Dispose() Implements IDisposable.Dispose
        Throw New NotImplementedException()
    End Sub
End Class
Class MainWindow

End Class

RogerSchlueter-7899 1,446 Reputation points

2023-01-19T18:09:48.4533333+00:00

Thanks a lot for looking into this for me. Unfortunately, doing a rebuild didn't solve the problem for me.

But I'm not surprised because looking at the CommunityToolkit.Mvvm in the Object Browser, I could not find a public method named SetProperty. Where is that method in the CommunityToolkit.Mvvm in your example? Or is it somewhere else?

Here is a peek at my NuGet page:
RogerSchlueter-7899 1,446 Reputation points

2023-01-19T18:17:10.5933333+00:00

A related matter: If I read the documentation correctly, in order to use the built in capabilities of the Toolkit, properties must be decorated with <ObservableProperty> Is that your understanding?

Accepted answer

2 additional answers

Your answer

Hui Liu-MSFT 48,676 Reputation points Microsoft External Staff

2023-01-19T03:16:20.3566667+00:00

Hi,@Roger Schlueter. I use the following code, right -click the project for rebuild, and the error disappears. Did I miss something? If you have any questions, please provide more details.

Imports CommunityToolkit.Mvvm.ComponentModel Imports CommunityToolkit.Mvvm.Input Imports System.Data Imports System.Data.SqlClient Imports System.IO Public Class MainWindowVM Inherits ObservableObject Implements IDisposable Private _SelectedValue As String Public Property SelectedValue As String Get Return _SelectedValue End Get Set(value As String) SetProperty(_SelectedValue, value) End Set End Property Public Sub Dispose() Implements IDisposable.Dispose Throw New NotImplementedException() End Sub End Class Class MainWindow End Class
RogerSchlueter-7899 1,446 Reputation points

2023-01-19T18:09:48.4533333+00:00

Thanks a lot for looking into this for me. Unfortunately, doing a rebuild didn't solve the problem for me.

But I'm not surprised because looking at the CommunityToolkit.Mvvm in the Object Browser, I could not find a public method named SetProperty. Where is that method in the CommunityToolkit.Mvvm in your example? Or is it somewhere else?

Here is a peek at my NuGet page:
RogerSchlueter-7899 1,446 Reputation points

2023-01-19T18:17:10.5933333+00:00

A related matter: If I read the documentation correctly, in order to use the built in capabilities of the Toolkit, properties must be decorated with <ObservableProperty> Is that your understanding?

Answer 1

Michael Taylor 60,161

SetProperty is a protected method on the ObservableObject class.

I notice in your file that you're missing an Import CommunityToolkit.Mvvm.ComponentModel statement. The ObservableObject type is defined there. Without that import then the compiler cannot figure out your base type and hence SetProperty isn't available. That is the root of your issue I believe. You're seeing a cascading compiler error.

If the editor is showing ObservableObject as being defined then it isn't coming from the toolkit and that is causing the problem instead. Right click the type and go to definition. You should end up in the toolkit metadata. If you end up elsewhere then you have multiple types with the same name.

RogerSchlueter-7899 1,446 Reputation points

2023-01-19T22:55:50.64+00:00

Michael, the missing Import is only due to sloppy copy & paste. It is there. Sorry for the flub.
Michael Taylor 60,161 Reputation points

2023-01-20T00:18:29.45+00:00

Go to Definition on the ObservableObject. Please confirm it is mapping to the correct type and you should be able to see the type members. The SetProperty protected methods (there are 2) should be there.
RogerSchlueter-7899 1,446 Reputation points

2023-01-20T17:31:14.81+00:00

Excellent logic, Michael. Before I decided to use the Toolkit, I had created my own ObservableObject so, of course, the references were still using that instead of the Toolkit one. So I deleted my own ObservableObject.

Now when I use Go To Definition I see this in the Object Browser:

which still does not show a SetProperty method. Then, out of frustration, I used Peek Definition and sure enough, SetProperty is one of the methods. Yeah, problem solved .... but I'm still a bit in the dark: why does the Object Browser not show the SetProperty methods. Until now I thought the Object Browser was the place to go to see what properties and methods were available but apparently not. Can you please explain this ... and thanks a lot.
Michael Taylor 60,161 Reputation points

2023-01-20T18:37:41.0066667+00:00

SetProperty is a protected method on ObservableObject. Therefore only derived types have access to it. Go to the settings in this dialog and ensure that you're showing proected and inherited members.

To be honest Object Browser was a great tool in the C++ days when Intellisense was not up to par. But with .NET (and especially Roslyn) I don't use Object Browser at all anymore. To see the members available on a type I either Go to Definition on it or just this. to pull up the Intellisense list. You should see SetProperty at that point assuming you are inside a type that derives from ObservableObject.

Answer 2

@Michael_Taylor I do not agree with this answer. I am using CommunityToolkit.Mvvm.ComponentModel and I get very odd results. If I make a change to a view model where I have any ObservableProperty properties defined, it simply stops running any analyzers or doing any sort of code generation.

When I see the red squiggly line of death, all I do is close the solution and reopen it. This forces the analyzers to run and the missing properties get resolved.

So, it is not a matter of a missing component in the using definitions, it is something in the process of running or rerunning the analyzers. This is VERY annoying...........

Answer 3

@Michael_Taylor I do not agree with this answer. I AM using CommunityToolkit.Mvvm.ComponentModel and I get very odd behavior. If I make a change to a view model where I have any ObservableProperty properties defined, it simply stops running any analyzers or doing any sort of code generation. If I am correct, it stopped working when I updated my version from the prerelease version to 8.1.0

When I see the red squiggly line of death, all I do is close the solution and reopen it. This forces the analyzers to run and the missing properties get resolved. If I tried to do a build before closing the solution, it does not build, but upon simply reopening the solution, it will build without doing anything...

So, IMO it is not a matter of a missing component in the using definitions (or it could be in the case of the original post), it is something in the process of running or rerunning the analyzers. They stop running... In fact, it looks like the partial classes that are generated by the analyzers get deleted or corrupted somehow. There is still some investigation and debugging on the CommunityToolkit.MVVM side of things required. This is VERY annoying...........

Michael Taylor 60,161 Reputation points

2023-01-23T03:21:47.2133333+00:00

Your problem is not related to the OP's problem. The issue they were having was a simple compilation issue where the compiler was not finding a member that was declared on the base type. There issue was resolved by removing the incorrect base type.

The problem you are describing sounds like it is related to code that is automatically generated at compilation. That wasn't the case here as the member in question is not auto-generated by the compiler. I recommend you create your own post and report the issue as it is not the same problem as this thread I believe.

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CommunityToolkit.Mvvm Not Exposing Any Methods

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