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Foreword:

Before .NET 6, implementing file upload was simple:

[HttpPost ("upload")] public async Task Upload (IFormFile file) {/ / a pair of file performs return Ok (file.FileName);}

However, when you use the minimum WEB API of .NET 6 to achieve the same functionality, you encounter a lot of holes unexpectedly.

I. implementation code

After converting to a minimum WEB API to implement, the code looks like this:

App.MapPost ("/ upload", async (IFormFile file) = > {return Results.Ok (file.FileName);})

However, a HTTP 415error is returned when calling with the same client code:

Second, allow Content Type

This is because the Content-Type used when uploading files is not the default application/json, but multipart/form-data

In dotnet/aspnetcore 's issues, we found the relevant solution:

Modify the code as follows:

App.MapPost ("/ upload", async (IFormFile file) = > {return Results.Ok (file.FileName);}) .Accepts ("multipart/form-data")

As a result, a 415 error was returned. Even weirder, there is an extra stack of error messages:

Third, the emergence of BUG

Therefore, I want to find the problem by looking at the code.

Using the error message "Expected a supported JSON media type but got", we located the source code file Http/Http.Extensions/src/RequestDelegateFactory.cs:

However, there is a big difference in the code between the master branch and the v6.0.0 branch. For example, the master branch has IFormFile-related code, but not at all on v6.0.0:

Looking at the submission history of the file, we found a submission like this:

Based on the submission, we found the corresponding issue:

It seems that to support the IFormFile parameter, we will have to wait until November 2022 (the expected release date of .NET 7)!

IV. Solution

Fortunately, the issue also provides a workaround solution, passing in the HttpRequest parameter:

App.MapPost ("/ upload", async (HttpRequest request) = > {var form = await request.ReadFormAsync (); return Results.Ok (form.Files.First () .filename);})

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