Partial ObservableProperty in ObservableObject shows error CS0229 ambiguity between property and property

[jpageacsys]

Describe the bug

I'm developing a WinUI application with Community Toolkit MVVM 8.4.0.
I switched the properties in my application to use the new format. Here's one example:

[ObservableProperty]
public partial bool Returned { get; set; } = returned;

And this is a simplified version of the constructor for the object:
public partial class Item(bool returned) : ObservableObject

This all works as expected and compiles fine but all uses of the property elsewhere show the Compiler Error CS0229. In this case it shows:
Ambiguity between Item.Returned and Item.Returned.
I only have the one property called Returned.
As I said, it all compiles fine and works correctly but I'm not able to get rid of the error.

Regression

No response

Steps to reproduce

Create a class with the type ObservableObject and create a partial Observable Property. Use it elsewhere in the app.

Example:

public partial class Item(bool returned) {
    [ObservableProperty]
    public partial bool Returned { get; set; } = returned;
}

Then access the property somewhere else in the app.

Example:

var newItem = new Item(false);
newItem.Returned = true;

This shows the compiler error.

Expected behavior

I would like to remove the false alarm.

Screenshots

IDE and version

VS 2022

IDE version

Version 17.13.1

Nuget packages

• CommunityToolkit.Common
• CommunityToolkit.Diagnostics
• CommunityToolkit.HighPerformance
• CommunityToolkit.Mvvm (aka MVVM Toolkit)

Nuget package version(s)

8.4.0

Additional context

No response

Help us help you

Yes, but only if others can assist

[masonritchason]

Confirmation

I am also experiencing this issue in the same conditions.

Steps to Reproduce

I have an ObservableProperty named FullName defined in an ObservableObject extending class Process.cs, as defined below:

/// <summary>
/// [Observable] A reference-friendly Process name in the form of "Code-Title".
/// </summary>
[ObservableProperty]
public partial string FullName {get; set;} = $"{Code}-{Title}";

When I attempt to access this property in my ViewModel class, like so:

/// <summary>
/// Serves the Process masterlist as a list of Process Full Name strings.
/// </summary>
public List<string> ProcessNames {
    get => Processes.Select(x => x.FullName).ToList();
}

My IDE shows this error:

Ambiguity between 'Process.FullName' and 'Process.FullName' CS0229
string Process.FullName { get; set; }
'FullName' is not null here.

Environment Details

IDE:

Visual Studio Code

Version: 1.98.2 (user setup)
Commit: ddc367ed5c8936efe395cffeec279b04ffd7db78
Date: 2025-03-12T13:32:45.399Z
Electron: 34.2.0
ElectronBuildId: 11161602
Chromium: 132.0.6834.196
Node.js: 20.18.2
V8: 13.2.152.36-electron.0
OS: Windows_NT x64 10.0.26100

CommunityToolkit:

<PackageReference Include="CommunityToolkit.Maui" Version="11.1.0" />
<PackageReference Include="CommunityToolkit.Mvvm" Version="8.4.0" />

.NET Info:

.NET SDK:
 Version:           9.0.104
 Commit:            2750432faa
 Workload version:  9.0.100-manifests.5c4e24dc
 MSBuild version:   17.12.27+e0b90a9a8

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.26100
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\9.0.104\

.NET workloads installed:
 [maui]
   Installation Source: SDK 9.0.100
   Manifest Version:    9.0.14/9.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\9.0.100\microsoft.net.sdk.maui\9.0.14\WorkloadManifest.json
   Install Type:              Msi

Configured to use loose manifests when installing new manifests.

Host:
  Version:      9.0.3
  Architecture: x64
  Commit:       831d23e561

.NET SDKs installed:
  9.0.104 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 9.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

[Sergio0694]

"This all works as expected and compiles fine but all uses of the property elsewhere show the Compiler Error CS0229"

That's very weird. I also can't repro and I never saw this happen.
@CyrusNajmabadi do you think this might be an IDE bug? Should they report this in VS Feedback?

[masonritchason]

Confirmation

I am also experiencing this issue in the same conditions.

...

Update

Oddly enough, I have another ObservableObject, Part.cs, with identical implementation. When I attempt to reference this class, I can. I'm including the source for each of these classes to compare.

Class Implementations

Process.cs:

using CommunityToolkit.Mvvm.ComponentModel;

namespace LotCoMPrinter.Models.Datasources;

...
public partial class Process(string Code, string Title, string Type, List<Part> Parts): ObservableObject {
    ...
    [ObservableProperty]
    public partial string Code {get; set;} = Code;

    ...
    [ObservableProperty]
    public partial string Title {get; set;} = Title;

    ...
    [ObservableProperty]
    public partial string FullName {get; set;} = $"{Code}-{Title}";

    ...
    [ObservableProperty]
    public partial string Type {get; set;} = Type;

    ...
    [ObservableProperty]
    public partial List<Part> Parts {get; set;} = Parts;
}

Part.cs

using CommunityToolkit.Mvvm.ComponentModel;

namespace LotCoMPrinter.Models.Datasources;

...
public partial class Part(string ParentProcess, string PartNumber, string PartName, string ModelNumber): ObservableObject {
    ...
    [ObservableProperty]
    public partial string ParentProcess {get; set;} = ParentProcess;

    ...
    [ObservableProperty]
    public partial string PartNumber {get; set;} = PartNumber;

    ...
    [ObservableProperty]
    public partial string PartName {get; set;} = PartName;

    ...
    [ObservableProperty]
    public partial string ModelNumber {get; set;} = ModelNumber;
}

Conditions of Functioning Reference

This method, in my ViewModel class, is able to reference Part.ModelNumber (via the SelectedPart property with type Part):

...
private async Task<Tuple<string, List<string>>> SerializeLabel(...) {
    ...
    // serialize the label if needed
    // This reference to SelectedProcess (type Process) throws IDE warning
    if (SelectedProcess!.Type.Equals("Originator")) {  
        string? SerialNumber;
        // assign/retrieve a cached serial number for this label
        // This reference does not throw IDE warning
        SerialNumber = await Serializer.Serialize(UICapture[1].Replace("Part: ", ""), SelectedPart!.ModelNumber, SerializeMode, BasketType);
        ...
    }
    ...
}

[masonritchason]

That's very weird. I also can't repro and I never saw this happen. @CyrusNajmabadi do you think this might be an IDE bug? Should they report this in VS Feedback?

@Sergio0694
I have a feeling it may be. I tried to run my app, ignoring the problem warnings. The app builds and runs with no related warnings or errors.

[jpageacsys]

Looks like updating to Visual Studio 2022 preview 17.14 fixes this issue:
dotnet/roslyn#76949

[RainerWingel]

I have the same bug in VS Community v17.13.5