WPF App: CS0579 and CS0111 Build Errors

[markolbert]

I have a WPF app which used to build fine in December 2021 but is now throwing errors I don't recall seeing before and don't know how to resolve.

The CS0579 errors all stem from one file that appears to be generated by the toolkit:

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#pragma warning disable
namespace Microsoft.Toolkit.Mvvm.Messaging.__Internals
{
    [global::System.CodeDom.Compiler.GeneratedCode("Microsoft.Toolkit.Mvvm.SourceGenerators.IMessengerRegisterAllGenerator", "7.1.0.0")]
    [global::System.Diagnostics.DebuggerNonUserCode]
    [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
    [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
    [global::System.Obsolete("This type is not intended to be used directly by user code")]
    internal static partial class __IMessengerExtensions
    {
        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
        [global::System.Obsolete("This method is not intended to be called directly by user code")]
        public static global::System.Action<IMessenger, object> CreateAllMessagesRegistrator(global::J4JSoftware.RetirementModeling.CategoryStatsVM _)
        {
            static void RegisterAll(IMessenger messenger, object obj)
            {
                var recipient = (global::J4JSoftware.RetirementModeling.CategoryStatsVM)obj;
                messenger.Register<global::J4JSoftware.RetirementModeling.CachedDatabaseMessage>(recipient);
            }

            return RegisterAll;
        }

        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
        [global::System.Obsolete("This method is not intended to be called directly by user code")]
        public static global::System.Action<IMessenger, object, TToken> CreateAllMessagesRegistratorWithToken<TToken>(global::J4JSoftware.RetirementModeling.CategoryStatsVM _)
            where TToken : global::System.IEquatable<TToken>
        {
            static void RegisterAll(IMessenger messenger, object obj, TToken token)
            {
                var recipient = (global::J4JSoftware.RetirementModeling.CategoryStatsVM)obj;
                messenger.Register<global::J4JSoftware.RetirementModeling.CachedDatabaseMessage, TToken>(recipient, token);
            }

            return RegisterAll;
        }
    }
}

The CS0579 errors are asserting the various attributes on that partial class are duplicates.

The CS0111 errors are showing up in other files generated by the toolkit. They come in pairs, two for each of 8 files in my project:

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#pragma warning disable
namespace Microsoft.Toolkit.Mvvm.Messaging.__Internals
{
    internal static partial class __IMessengerExtensions
    {
        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
        [global::System.Obsolete("This method is not intended to be called directly by user code")]
        public static global::System.Action<IMessenger, object> CreateAllMessagesRegistrator(global::J4JSoftware.RetirementModeling.IncExpStatsVM _)
        {
            static void RegisterAll(IMessenger messenger, object obj)
            {
                var recipient = (global::J4JSoftware.RetirementModeling.IncExpStatsVM)obj;
                messenger.Register<global::J4JSoftware.RetirementModeling.IncomeExpensesChangedMessage>(recipient);
            }

            return RegisterAll;
        }

        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
        [global::System.Obsolete("This method is not intended to be called directly by user code")]
        public static global::System.Action<IMessenger, object, TToken> CreateAllMessagesRegistratorWithToken<TToken>(global::J4JSoftware.RetirementModeling.IncExpStatsVM _)
            where TToken : global::System.IEquatable<TToken>
        {
            static void RegisterAll(IMessenger messenger, object obj, TToken token)
            {
                var recipient = (global::J4JSoftware.RetirementModeling.IncExpStatsVM)obj;
                messenger.Register<global::J4JSoftware.RetirementModeling.IncomeExpensesChangedMessage, TToken>(recipient, token);
            }

            return RegisterAll;
        }
    }
}

The errors assert that these generated methods duplicate existing ones:

CS0111 Type '__IMessengerExtensions' already defines a member called 'CreateAllMessagesRegistratorWithToken' with the same parameter types RetirementWPF C:\Programming\Archive\RetirementModeling\RetirementWPF\Microsoft.Toolkit.Mvvm.SourceGenerators\Microsoft.Toolkit.Mvvm.SourceGenerators.IMessengerRegisterAllGenerator\J4JSoftware.RetirementModeling.IncExpStatsVM.cs 24 Active

Any clues as to what may be going wrong and how to fix it would be most appreciated.

• Mark

[niels9001]

Hi @markolbert , the Windows Community Toolkit only works with UWP and WinUI3 - not WPF.

The .NET MVVM Toolkit is the successor of the Windows Community MVVM package. This one is framework agnostic and will work with WPF: https://docs.microsoft.com/en-us/dotnet/communitytoolkit/mvvm/

[michael-hawker]

Seems like this may be a duplicate of #343

[michael-hawker]

See dotnet/wpf#6792