Generic type constraints always gives The type or namespace name ... could not be found

[304NotModified]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I'm trying dotnet/aspnetcore#31800

This will always get a build error when using @typeparam T where T:IProductModel

CS0246 The type or namespace name 'IProductModel' could not be found (are you missing a using directive or an assembly reference?)

There are no intellisense errors

I tried:

• using the full namespace
• adding the namespace with @using
• adding the namespace to _Imports.razor

Expected Behavior

No build error

Steps To Reproduce

I have this interface (in the same project as my Blazor Server)

public interface IProductModel
{
    int Code { get; }

    string Description { get; }
}

I have this component (stripped version)

@typeparam T where T:IProductModel

<select class="form-select">
	@foreach (var item in Items)
	{
		<option value="@item.Code" selected="@(item.Code == Selected.Code)">@item.Description</option>
	}
</select>
@code {
	[Parameter]
	public T Selected { get; set; } = default!;

	[Parameter]
	public IEnumerable<T> Items { get; set; } = default!;
}

Build the code.

See #7105

Exceptions (if any)

Only build errors

.NET Version

6.0.302

Anything else?

• Visual Studio 2022 v17.2.6
• Blazor Server .NET 6

[javiercn]

@304NotModified thanks for contacting us. This could be a dupe of #7103

Could you provide a minimal repro project that demonstrates the issue?

Hi @304NotModified. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[304NotModified]

Yes I will try a repro case!

[304NotModified]

Repro project

See https://github.com/304NotModified/BlazorTypeParamBug

branch main

this is just the starter template (dotnet new blazorserver) and added this commit: 304NotModified/BlazorTypeParamBug@77df631

dotnet build gives the error, see:

D:\vs\Blazor-repo [main]> dotnet build
Microsoft (R) Build Engine version 17.2.0+41abc5629 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  All projects are up-to-date for restore.
D:\vs\Blazor-repo\Microsoft.NET.Sdk.Razor.SourceGenerators\Microsoft.NET.Sdk.Razor.SourceGenerators.RazorSourceGenerator\Page s_Index_razor.g.cs(126,23): error CS0246: The type or namespace name 'IMyInterface' could not be found (are you missing a usi ng directive or an assembly reference?) [D:\vs\Blazor-repo\Blazor-repo.csproj]

Build FAILED.

D:\vs\Blazor-repo\Microsoft.NET.Sdk.Razor.SourceGenerators\Microsoft.NET.Sdk.Razor.SourceGenerators.RazorSourceGenerator\Page s_Index_razor.g.cs(126,23): error CS0246: The type or namespace name 'IMyInterface' could not be found (are you missing a usi ng directive or an assembly reference?) [D:\vs\Blazor-repo\Blazor-repo.csproj]
    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:06.93

IntelliSense works correctly:

[304NotModified]

work around:

<MyComponent1 Item="myItem"></MyComponent1>

=>

<MyComponent1 Item="myItem" T="IMyInterface"></MyComponent1>

[chsienki]

Duplicate of #7080

[304NotModified]

Sounds a bit waste of my time to create a repo case...