IFormFile incompatible with FromForm in Minimal APIs for .NET 8 Preview 6

[gavilanch]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

In ASP.NET Core 8 - Preview 6. When applying a FromForm attribute to a class with an IFormFile property, when doing the HTTP request, the app throws an InvalidOperationException: No converter registered for type 'Microsoft.AspNetCore.Http.IFormFile'.

Expected Behavior

This shouldn't throw an exception, but assign the value to the corresponding IFormFile property.

Steps To Reproduce

Github repo: https://github.com/gavilanch/TestFromFormDotNet8Preview6/tree/master

The repo basically have 2 important files: Program.cs and CreateActorDTO.cs. The second one is a DTO with a string and IFormFile property. I have included an endpoint with a form so that you can easily test the behavior.

Exceptions (if any)

System.InvalidOperationException: No converter registered for type 'Microsoft.AspNetCore.Http.IFormFile'.
   at Microsoft.AspNetCore.Components.Endpoints.Binding.FormDataMapperOptions.CreateConverter(Type type, FormDataMapperOptions options)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd[TArg](TKey key, Func`3 valueFactory, TArg factoryArgument)
   at Microsoft.AspNetCore.Components.Endpoints.Binding.ComplexTypeConverterFactory.CanConvert(Type type, FormDataMapperOptions options)
   at Microsoft.AspNetCore.Components.Endpoints.Binding.FormDataMapperOptions.<>c.<.ctor>b__2_4(Type type, FormDataMapperOptions options)
   at Microsoft.AspNetCore.Components.Endpoints.Binding.FormDataMapperOptions.CreateConverter(Type type, FormDataMapperOptions options)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd[TArg](TKey key, Func`3 valueFactory, TArg factoryArgument)
   at Microsoft.AspNetCore.Components.Endpoints.Binding.FormDataMapperOptions.ResolveConverter[T]()
   at lambda_method3(Closure, Object, HttpContext, Object)
   at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass102_2.<<HandleRequestBodyAndCompileRequestDelegateForForm>b__2>d.MoveNext()
--- End of stack trace from previous location ---
   at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
   at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

HEADERS
=======
Accept: */*
Connection: keep-alive
Host: localhost:7085
User-Agent: PostmanRuntime/7.32.3
Accept-Encoding: gzip, deflate, br
Content-Type: multipart/form-data; boundary=--------------------------393630075424756012793498
Content-Length: 208566
Postman-Token: dcac1cc6-03f4-4bd5-9a75-3a4be032efff

.NET Version

8.0.100-preview.6.23330.14

Anything else?

ASP.NET Core Version: 8.0.0-preview.6.23329.11

IDE: Microsoft Visual Studio Community 2022 (64-bit) - Preview
Version 17.7.0 Preview 4.0
Windows 10

dotnet --info:

.NET SDK:
 Version:   8.0.100-preview.6.23330.14
 Commit:    ba97796b8f

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19043
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\8.0.100-preview.6.23330.14\

.NET workloads installed:
There are no installed workloads to display.

Host:
  Version:      8.0.0-preview.6.23329.7
  Architecture: x64
  Commit:       5340be2ccc

.NET SDKs installed:
  5.0.408 [C:\Program Files\dotnet\sdk]
  7.0.101 [C:\Program Files\dotnet\sdk]
  7.0.304 [C:\Program Files\dotnet\sdk]
  7.0.400-preview.23330.10 [C:\Program Files\dotnet\sdk]
  8.0.100-preview.6.23330.14 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 8.0.0-preview.6.23329.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.0-preview.6.23329.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.18 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.19 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.8 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.0-preview.6.23329.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  Not set

global.json file:
  Not found

[captainsafia]

@gavilanch Thanks for reporting this bug!

We recently added support for complex form binding to minimal APIs. It kicks in when a parameter has a FromForm attribute. We should probably add another check to verify that it only kicks in on complex types that aren't IFormFile/IFormCollection/etc.

[captainsafia]

As I was looking at this, I missed a key detail in the repro which is the fact that the IFormFile type is encapsulated in another type. As a result of this, the description that I gave earlier for this bug isn't totally valid.

I believe that we might need to modify the form-binding behavior here to provide more direct converters for certain form-related primitives (e.g. IFormFile, IFormCollection, etc)

cc: @javiercn

[Markz878]

My ticket 50614 was closed as a dupe of this, but in RC2 I still can't bind a Blazor SSR form to an IFormFile property. Could someone clarify this? @mkArtakMSFT @captainsafia

[captainsafia]

@Markz878 Sure! This was closed as a dupe because the napping logic is shared between minimal APIs and Blazor here. The PR referenced above contains tests showcasing Blazor usage. Can you share a repro of the code that's not working as desired?