[ObservableProperty] - error CS0103: The name '{Property}' does not exist in the current context

[lemonlad]

Describe the bug

I receive the build-time error:

CS0103: The name '{Property}' does not exist in the current context upon building when using [ObservableProperty] and trying to set the generated property

namespace WpfApp1_TestMVVMToolKit.ViewModels
{
    public partial class MainWindowViewModel : ObservableObject
    {
        [ObservableProperty]
        private string title;

        private void DoSomething()
        {

            Title = "a";
        }
    }

}

Regression

No response

Steps to reproduce

• Create WPF App (.NET Framework 4.7.2)
• Add package CommunityToolkit.Mvvm 8.0.0-preview4
• Add below code to a class

namespace WpfApp1_TestMVVMToolKit.ViewModels
{
    public partial class MainWindowViewModel : ObservableObject
    {
        [ObservableProperty]
        private string title;

        private void DoSomething()
        {

            Title = "a";
        }
    }

}

Build, build fails with error:

error CS0103: The name 'Title' does not exist in the current context

Intellisense does not pick up that Title property exists

Roll back to CommunityToolkit.Mvvm 7.1.2

Build, fails with error:

error CS0103: The name 'Title' does not exist in the current context

In 7.1.2, although build still fails, intellisense does pick up that the Title property exists, with generated code as below:

namespace WpfApp1_TestMVVMToolKit.ViewModels
{
    public partial class MainWindowViewModel
    {
        [global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", "7.1.0.0")]
        [global::System.Diagnostics.DebuggerNonUserCode]
        [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
        public string Title
        {
            get => title;
            set
            {
                if (!global::System.Collections.Generic.EqualityComparer<string>.Default.Equals(title, value))
                {
                    OnPropertyChanging(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedOrChangingArgs.TitlePropertyChangingEventArgs);
                    title = value;
                    OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedOrChangingArgs.TitlePropertyChangedEventArgs);
                }
            }
        }
    }
}

Expected behavior

I expect to be able to use the generated Title property, and for OnPropertyChanged to fire automatically when changing the value

Screenshots

No response

IDE and version

VS 2022

IDE version

17.2.3

Nuget packages

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

Nuget package version(s)

7.1.2, 8.0.0-preview4

Additional context

No response

Help us help you

No, just wanted to report this

[Sergio0694]

Duplicate of #158, this is a known issue with .NET Framework non-SDK-style WPF projects.
You'll have to either move that code to a .NET Standard library, or upgrade to an SDK-style .NET 6 WPF project.

[mklemarczyk]

@Sergio0694 it does not work in last .NET 9 with project in SDK style WPF project.

Because of issue dotnet/wpf#10068