ASPNetCore API IFormFile returning "invalid input"

Question

I have an api and i'm trying to upload an image. I tried using swagger & postman.

All i'm getting back is

{
    "": [
        "The input was not valid."
    ]
}

This is how my code looks like ->

Controller -

    [HttpPost("images")]
    public async Task<IActionResult> UploadImage(IFormFile file)
    {
        return await _imageHandler.UploadImage(file);
    }

Image Handler -

public interface IImageHandler
{
    Task<IActionResult> UploadImage(IFormFile file);
}

public class ImageHandler : IImageHandler
{
    private readonly IImageWriter _imageWriter;
    public ImageHandler(IImageWriter imageWriter)
    {
        _imageWriter = imageWriter;
    }

    public async Task<IActionResult> UploadImage(IFormFile file)
    {
        var result = await _imageWriter.UploadImage(file);
        return new ObjectResult(result);
    }
}

And finally image writer

public class WriterHelper
{
    public enum ImageFormat
    {
        bmp,
        jpeg,
        gif,
        tiff,
        png,
        unknown
    }

    public static ImageFormat GetImageFormat(byte[] bytes)
    {
        var bmp = Encoding.ASCII.GetBytes("BM");     // BMP
        var gif = Encoding.ASCII.GetBytes("GIF");    // GIF
        var png = new byte[] { 137, 80, 78, 71 };              // PNG
        var tiff = new byte[] { 73, 73, 42 };                  // TIFF
        var tiff2 = new byte[] { 77, 77, 42 };                 // TIFF
        var jpeg = new byte[] { 255, 216, 255, 224 };          // jpeg
        var jpeg2 = new byte[] { 255, 216, 255, 225 };         // jpeg canon

        if (bmp.SequenceEqual(bytes.Take(bmp.Length)))
            return ImageFormat.bmp;

        if (gif.SequenceEqual(bytes.Take(gif.Length)))
            return ImageFormat.gif;

        if (png.SequenceEqual(bytes.Take(png.Length)))
            return ImageFormat.png;

        if (tiff.SequenceEqual(bytes.Take(tiff.Length)))
            return ImageFormat.tiff;

        if (tiff2.SequenceEqual(bytes.Take(tiff2.Length)))
            return ImageFormat.tiff;

        if (jpeg.SequenceEqual(bytes.Take(jpeg.Length)))
            return ImageFormat.jpeg;

        if (jpeg2.SequenceEqual(bytes.Take(jpeg2.Length)))
            return ImageFormat.jpeg;

        return ImageFormat.unknown;
    }
}

I was following this tutorial -> https://www.codeproject.com/Articles/1256591/Upload-Image-to-NET-Core-2-1-API

I've already modified Swagger in the project to be able to upload files, but even swagger throws the same error. I got no other errors in my code & debugging does nothing (trying to set breakpoints in my controller, but apparently they dont take or they aren't supposed to, still learning here).

Any help will be appreciated. Thanks!

Did a clean test and the problem seems to be in [ApiController]. Any idea why/how i can fix it?

Answer 1

Found my problem and found my fix. After finding that my problem was [ApiController] i stumbled upon another stackoverflow problem related to this.

This fixed my problem. Modifyingservices.AddMvc() to -> services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);