Swashbuckle : Allow file import through the Swagger UI

One of the API’s I’m building allows you to import files to a database.

	[Route("api/")]
	public class FileController : Controller
	{
	private readonly IFileService _fileService;
	public FileController(IFileService fileService)
	{
	_fileService = fileService;
	}
	// POST api/values
	[HttpPost("")]
	[ProducesResponseType(StatusCodes.Status201Created)]
	public async Task<IActionResult> Post(IFormFile file)
	{
	var uploadFileModel=new UploadFileModel()
	{
	FileName = file.FileName,
	ContentType = file.ContentType,
	Data = file.ConvertToByteArray()
	};
	var fileLocation=await _fileService.UploadFile(uploadFileModel);
	return CreatedAtAction("GetByIdAndVersion", new {id = fileLocation.Id,version=fileLocation.Version, fileName=file.FileName},null);
	}
	}

view raw FileController.cs hosted with ❤ by GitHub

To simplify testing I wanted to allow the consumers of my API to test the API directly through the Swagger UI. Problem is that out of the box Swashbuckle(the Swagger implementation for .NET) has no clue how to interprete the IFormFile.

Let’s fix that by introducing an IOperationFilter:

	public class FileOperationFilter : IOperationFilter
	{
	public void Apply(Operation operation, OperationFilterContext context)
	{
	if (context.ApiDescription.ParameterDescriptions.Any(x => x.ModelMetadata.ModelType == typeof(IFormFile)))
	{
	operation.Parameters.Clear();
	operation.Parameters.Add(new NonBodyParameter
	{
	Name = "file", // must match parameter name from controller method
	In = "formData",
	Description = "Upload file.",
	Required = true,
	Type = "file"
	});
	operation.Consumes.Add("application/form-data");
	}
	}
	}

view raw FileOperationFilter.cs hosted with ❤ by GitHub

And let’s not forget to register that IOperationFilter in our Startup.cs file:

	public void ConfigureServices(IServiceCollection services)
	{
	services.AddSwaggerGen(c=>
	{
	c.SwaggerDoc("v1", new Info { Title = "File API", Version = "v1" });
	c.OperationFilter<FileOperationFilter>();
	});
	}

view raw Startup.cs hosted with ❤ by GitHub

Now if we run our application and browse to the swagger endpoint(/swagger), when we try to execute our Upload operation, we get a nice Import button: