CS0436 The type 'AssemblyReference' in 'path-to\IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the importet type of 'AssemblyReference' in 'path-to-GeneratedAssemblyReference-in-Application-Layer'...

[DevTKSS]

I am getting this CS0436 Warning in my (targeting to become ;) ) Clean Architecuture Project on Re-Building in VS2022/VS2026, but I don't know what is it what I am doing wrong. I did not create a dedicated AssemblyReference, so I would assume the Mediator Generator should also not provide this warning because it found some default dotnet/msbuild generated file...

Can somebody help me?

Output from `WebApi.csproj` Re-Build

4>------ Rebuild All started: Project: WebApi (src\WebAPI\WebApi), Configuration: Debug Any CPU ------
4>CSC : warning MSG0005: MediatorGenerator found message without any registered handler: DevTKSS.MyManufacturerERP.Domain.Common.BaseEvent
4>CSC : warning MSG0005: MediatorGenerator found message without any registered handler: DevTKSS.MyManufacturerERP.Domain.Events.TodoItemDeletedEvent
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\MediatorOptions.g.cs(41,82,41,99): warning CS0436: The type 'AssemblyReference' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the imported type 'AssemblyReference' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(36,127,36,142): warning CS0436: The type 'MediatorOptions' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\MediatorOptions.g.cs' conflicts with the imported type 'MediatorOptions' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\MediatorOptions.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs(29,41,29,58): warning CS0436: The type 'AssemblyReference' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the imported type 'AssemblyReference' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs(36,41,36,58): warning CS0436: The type 'AssemblyReference' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the imported type 'AssemblyReference' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(808,94,808,102): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(853,115,853,123): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\MediatorOptions.g.cs(41,149,41,166): warning CS0436: The type 'AssemblyReference' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the imported type 'AssemblyReference' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs(29,92,29,109): warning CS0436: The type 'AssemblyReference' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the imported type 'AssemblyReference' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs(36,111,36,128): warning CS0436: The type 'AssemblyReference' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs' conflicts with the imported type 'AssemblyReference' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\AssemblyReference.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(38,45,38,60): warning CS0436: The type 'MediatorOptions' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\MediatorOptions.g.cs' conflicts with the imported type 'MediatorOptions' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\MediatorOptions.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(52,121,52,129): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(52,156,52,164): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(53,181,53,189): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(54,179,54,187): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs(55,182,55,190): warning CS0436: The type 'Mediator' in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs' conflicts with the imported type 'Mediator' in 'DevTKSS.MyManufacturerERP.Application, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Using the type defined in 'C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\obj\Debug\net10.0\Mediator.SourceGenerator\Mediator.SourceGenerator.IncrementalMediatorGenerator\Mediator.g.cs'.
4>  WebApi -> C:\Users\Sonja\source\repos\DevTKSS.MyManufacturerERP\src\WebApi\WebApi\bin\Debug\net10.0\DevTKSS.MyManufacturerERP.WebApi.dll

(WebAPI.csproj uses the same packages as Application.csproj, just the ProjectReference is set to ..\Application\Application.csproj instead of ..\Domain\Domain.csproj)

the Application.csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>$(DefaultTargetFramework)</TargetFrameworks> <!-- DefaultTargetFramework is set to net10.0 -->
    <RootNamespace>DevTKSS.MyManufacturerERP.Application</RootNamespace>
    <AssemblyName>DevTKSS.MyManufacturerERP.Application</AssemblyName>
  </PropertyGroup>

  <ItemGroup Label="Microsoft Packages">
    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" />
    <PackageReference Include="Microsoft.Extensions.Logging" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" />
  </ItemGroup>
  
  <ItemGroup>
    <PackageReference Include="Ardalis.GuardClauses" />
    <PackageReference Include="FluentValidation.DependencyInjectionExtensions" />
    <PackageReference Include="Mediator.Abstractions" />
    <PackageReference Include="Mediator.SourceGenerator" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\Domain\Domain.csproj" />
  </ItemGroup>
</Project>

and the Domain.csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>$(DefaultTargetFramework)</TargetFrameworks>
    <RootNamespace>DevTKSS.MyManufacturerERP.Domain</RootNamespace>
    <AssemblyName>DevTKSS.MyManufacturerERP.Domain</AssemblyName>
    <NoWarn>$(NoWarn);MSG0005</NoWarn> <!-- This does still produce the MSG on rebuild of WebApi 🙄 the Handler is defined in the Application Layer -->
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Mediator.Abstractions" />
    <PackageReference Include="Mediator.SourceGenerator" />
  </ItemGroup>
</Project>

Package Versions defined in the Directory.Packages.props file:

  <ItemGroup>
    <PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.0" />
    <PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.0" />
    <PackageVersion Include="Microsoft.Extensions.Logging" Version="10.0.0" />
    <PackageVersion Include="Microsoft.EntityFrameworkCore" Version="10.0.0" />
  </ItemGroup>
  <ItemGroup Label="CA Packages">
    <PackageVersion Include="Ardalis.GuardClauses" Version="5.0.0" />
    <PackageVersion Include="FluentValidation.DependencyInjectionExtensions" Version="12.1.1" />
    <PackageVersion Include="Mediator.Abstractions" Version="3.0.1" />
    <PackageVersion Include="Mediator.SourceGenerator" Version="3.0.1" />
  </ItemGroup>

[rm-code]

The README.md can be a bit misleading IMO. The important part is here:

https://github.com/martinothamar/Mediator?tab=readme-ov-file#3-usage-and-abstractions

You install the source generator package into your edge/outermost project (i.e. ASP.NET Core application, Background worker project)

use the Mediator.Abstractions package wherever you define message types and handlers

Don't install the SourceGenerator to all layers of your architecture. Only the "presentation" layer / outermost projects.

[martinothamar]

Yes, the source generator library generates the actual Mediator implementation and DI hooks. If you have multiple of those in the same deployed artifact its unclear what should happen 😄

The README.md can be a bit misleading IMO

Any tips on how to improve?

[rm-code]

Any tips on how to improve?

To be clear: This wasn't meant as a slight :) I think what tripped me up was this part of the docs:

Maybe just moving the clarifications up to that part would be enough:

Install the source generator package into your edge/outermost project (i.e. ASP.NET Core application, Background worker project)

dotnet add package Mediator.SourceGenerator --version 3.0.*

Install the Mediator.Abstractions package wherever you define message types and handlers

dotnet add package Mediator.Abstractions --version 3.0.*

[martinothamar]

Good point, thanks! Attempt at clarifications merged here: #269