System.InvalidOperationException: This request does not have a Content-Type header. Forms are available from requests with bodies like POSTs and a form Content-Type of either application/x-www-form-urlencoded or multipart/form-data

[BusHero]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

A minimal API post endpoint, that awaits form data generates 500 if the client sends a request to it with no form data

Expected Behavior

API should return 400?

Steps To Reproduce

https://github.com/BusHero/BugWithMinimalApi

Exceptions (if any)

System.InvalidOperationException: This request does not have a Content-Type header. Forms are available from requests with bodies like POSTs and a form Content-Type of either application/x-www-form-urlencoded or multipart/form-data.
         at Microsoft.AspNetCore.Http.Features.FormFeature.ReadForm()
         at lambda_method1(Closure, Object, HttpContext, Object)
         at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass104_2.<<HandleRequestBodyAndCompileRequestDelegateForForm>b__2>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

.NET Version

8.0

Anything else?

> dotnet --info
.NET SDK:
 Version:           8.0.204
 Commit:            c338c7548c
 Workload version:  8.0.200-manifests.9f663350

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.22635
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\8.0.204\

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

Host:
  Version:      8.0.4
  Architecture: x64
  Commit:       2d7eea2529

.NET SDKs installed:
  8.0.204 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 8.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.29 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.29 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

[captainsafia]

@BusHero Thanks for reporting this issue!

The exception that you're seeing comes from lower in the ASP.NET Core stack in the FormFeature when we eagerly attempt to read from the form body if we encounter a parameter that should bind from it.

We've made some changes to the form binding behavior in .NET 9 and I'm not able to repro the issue there. Can yo confirm the same using a 9.0-preview?

I'll put this in the backlog to gather signal on whether this is worth backporting.

[BusHero]

Hi @captainsafia. I can confirm that the issue is not reproducible using 9.0-preview.