Configuration binder generator creates namespace ambiguity error

[paulguz-datapa]

Description

After upgrading our ASP.Net 7 application (that started life as Core 1.1 and upgraded through several .Net Core versions) to .Net 8, when building in a DevOps pipeline, the following error happens:

BindingExtensions.g.cs(131,71): error CS0104: 'Options' is an ambiguous reference between 'myProject.Options' and 'Microsoft.Extensions.Options.Options'

According to the docs, the Configuration Binding Source Generator is disabled by default, yet we have needed to add <EnableConfigurationBindingGenerator>false</EnableConfigurationBindingGenerator> to the csproj to work around the error. We are not using AOT, and never have.

Note, the project references a Microsoft.NET.Sdk.BlazorWebAssembly project. I'm not sure if that's relevant.

Reproduction Steps

• Take an existing .Net 7 web project,
• put an Options class in the root namespace and use with WebApplicationBuilder.Services.Configure.
• Upgrade to .Net 8.
• Do not intentionally enable the Configuration-binding source generator.
• Do not use AOT

Expected behavior

Project should build successfully. Configuration-binding source generator should not be enabled.

Actual behavior

Project fails to build with the following error:

BindingExtensions.g.cs(131,71): error CS0104: 'Options' is an ambiguous reference between 'myProject.Options' and 'Microsoft.Extensions.Options.Options'

Configuration-binding source generator appears to be enabled despite it supposedly being disabled by default.

Regression?

No response

Known Workarounds

<EnableConfigurationBindingGenerator>false</EnableConfigurationBindingGenerator> in the csproj

Configuration

.Net 8

Other information

No response

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Issue Details

---

Description

After upgrading our ASP.Net 7 application (that started life as 1.1 and upgraded through several .Net Core versions) to .Net 8, when building in a DevOps pipeline, the following error happens:

BindingExtensions.g.cs(131,71): error CS0104: 'Options' is an ambiguous reference between 'myProject.Options' and 'Microsoft.Extensions.Options.Options'

According to the docs, the Configuration Binding Source Generator is disabled by default, yet we have needed to add false to the csproj to work around the error.

Reproduction Steps

• Take an existing .Net 7 web project,
• put an Options class in the root namespace and use with WebApplicationBuilder.Services.Configure.
• Upgrade to .Net 8.
• Do not intentionally enable the Configuration-binding source generator.

Expected behavior

Project should build successfully. Configuration-binding source generator should not be enabled.

Actual behavior

Project fails to build with the following error:

BindingExtensions.g.cs(131,71): error CS0104: 'Options' is an ambiguous reference between 'myProject.Options' and 'Microsoft.Extensions.Options.Options'

Configuration-binding source generator appears to be enabled despite it supposedly being disabled by default.

Regression?

No response

Known Workarounds

false in the csproj

Configuration

.Net 8

Other information

No response

Author:	paulguz-datapa
Assignees:	-
Labels:	area-Extensions-Configuration
Milestone:	-

[eerhardt]

Is PublishTrimmed set to true in your app? When a web application has PublishTrimmed or PublishAot set to true, the source generators are enabled in .NET 8. The idea is that when you are trimming, the source generators are the only way to guarantee config binding will work after trimming (or AOT).

See dotnet/aspnetcore#48416 and dotnet/sdk#34022.

However, if your app is a Blazor WASM app, it shouldn't be enabled by default.

https://github.com/dotnet/sdk/blob/601383646e1547c6bc77c3295be63ff3939b0f2e/src/BlazorWasmSdk/Targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets#L24-L25

[tarekgh]

@paulguz-datapa could you please provide a sample project reproduce the issue? or compile your app with /bl and share the produced msbuild logs.

This issue has been marked needs-author-action and may be missing some important information.

[tarekgh]

Also, #94267 maybe fixing the namespace ambiguity too. You may try the 8.0.2 builds from https://github.com/dotnet/installer or when you share a sample project, I can try it too.

CC @eiriktsarpalis @ericstj

[paulguz-datapa]

@eerhardt Yes, we are enabling PublishTrimmed.

@tarekgh There is a sample solutiuon here.