how to get swashbuckle to generate parameter type "form" for testing APIs that need a file upload?

[sladeVol]

I've been trying to figure this out for the last few days. I am writing an API that uploads a file (based it a upload file tutorial on the asp.net/web-api site) , but I cannot figure out how to list the file parameter in the signature so that swashbuckle can generate the appropriate parameter type for the swagger ui to render a "select a file" button instead of a text field. Is this a limitation to web api, swashbuckle or to .Net in general?

[domaindrivendev]

I'm assuming your file upload implementation is similar to this - http://www.asp.net/web-api/overview/advanced/sending-html-form-data,-part-2. Because all the "file upload" specifics are happening at run-time, there is no way for Swashbuckle to automatically generate a Parameter description with the relevant "file upload" details.

So, you need to tell it about this specific parameter. This can be easily done with a custom IOperationFilter which you can wire up as follows:

AddFileParamTypes.cs

public class AddFileParamTypes : IOperationFilter
{
    public void Apply(Operation operation, DataTypeRegistry dataTypeRegistry, ApiDescription apiDescription)
    {
        if (operation.Nickname == "FileUpload_PostFormData") // controller and action name
        {
            operation.Consumes.Add("multipart/form-data");
            operation.Parameters.Add(new Parameter
                {
                    Name = "file",
                    Required = true,
                    Type = "file",
                    ParamType = "form"
                }
            );
        }
    }
}

SwaggerConfig.cs

SwaggerSpecConfig.Customize(c =>
    {
        c.OperationFilter<AddFileParamTypes>();
        ...

[wadewegner]

Looks like IOperationFilter changed since the comments above. Here's the code that worked for me:

public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
{
    if (operation.operationId == "FileUpload_PostFormData")  // controller and action name
    {
        operation.consumes.Add("multipart/form-data");
        operation.parameters = new List<Parameter>
        {
            new Parameter
            {
                name = "file",
                required = true,
                type = "file",
            }
        };
    }
}

[centur]

The comment above is no longer valid. See #531 issue (and mentioned there #280)
Changing code to:

new Parameter
  {
    name = "file",
    @in = "formData",
    required = true,
    type = "file"
  }

will fix the issue.
It's worth to note that working FileUpload operation filter can be found here

[RehanSaeed]

Any ideas how to get an upload file button working in Ahoy (Swagger for ASP.NET Core). The above code does not do the trick. I raised the following issue domaindrivendev/Swashbuckle.AspNetCore#193

[glyons]

Using an attriubute so it can be added to more controllers

public class ImportFileParamType : IOperationFilter
{
[AttributeUsage(AttributeTargets.Method)]
public sealed class SwaggerFormAttribute : Attribute
{
public SwaggerFormAttribute(string name, string description)
{
Name =name;
Description = description;
}
public string Name { get; private set; }

        public string Description { get; private set; }
    }
    public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
    {
        var requestAttributes = apiDescription.GetControllerAndActionAttributes<SwaggerFormAttribute>();
        foreach (var attr in requestAttributes)
        {
                operation.parameters = new List<Parameter>
                {
                    new Parameter
                    {
                        description = attr.Description,
                        name = attr.Name,
                        @in = "formData",
                        required = true,
                        type = "file",
                    }
                };
                operation.consumes.Add("multipart/form-data");
        }
    }`

API Controller

` [Route("ImageUpload")]
[HttpPost]
[ImportFileParamType.SwaggerFormAttribute("ImportImage", "Upload image file")]
public async Task PostFormDataImage()
{

        // Check if the request contains multipart/form-data.
        if (!Request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
        }

        string root = System.Web.HttpContext.Current.Server.MapPath("~/App_Data");
        var provider = new MultipartFormDataStreamProvider(root);

        try
        {
            // Read the form data.
            await Request.Content.ReadAsMultipartAsync(provider);

            // This illustrates how to get the file names.
            foreach (MultipartFileData file in provider.FileData)
            {
                Trace.WriteLine(file.Headers.ContentDisposition.FileName);
                Trace.WriteLine("Server file path: " + file.LocalFileName);
            }
            return Request.CreateResponse(HttpStatusCode.OK);
        }
        catch (System.Exception e)
        {
            return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, e);
        }
    }`

[razonrus]

Thank you @glyons !
A fix for the case where you have other options besides the file, for example your url is /api/user/{id}/photo:

foreach (var attr in requestAttributes)
            {
                operation.parameters = operation.parameters ?? new List<Parameter>();
                operation.parameters.Add(new Parameter
                {
                    description = attr.Description,
                    name = attr.Name,
                    @in = "formData",
                    required = true,
                    type = "file",
                });
                operation.consumes.Add("multipart/form-data");
            }

[glyons]

nice one @razonrus

[AndrewBragdon]

It would be nicer to do this via attribute on the method, rather than in a central place

[heldersepu]

@AndrewBragdon I think one of the comments: #120 (comment) does exactly that

[xerikai]

I'm attempting to do what @glyons describes, but the code never seems to be executed when I simply add it as an attribute to the controller method.
This is what my controller method is looking like
[Route("PostDecryptionKey"), HttpPost, Shared.Models.ImportFileParamType.SwaggerForm("DecryptionKey","Upload Decryption Key")]
public async Task PostDecryptionKey([FromBody] string GroupID)

I ONLY created the attribute and decorated the controller with it, so if I was supposed to do something in the swaggerconfig, that may be what I'm missing.

When I refactored it to be closer to what domaindrivendev suggested (including the swaggerconfig modification) then it works perfectly, but then I have to keep hardcoding a dependency on the operationID which I'd prefer not to do that.

I appreciate anyone who can chime in, :)

[heldersepu]

@xerikai see my commit, that is exactly what @glyons describes + @razonrus suggestion.
the final product is:
http://swashbuckletest.azurewebsites.net/swagger/ui/index?filter=Png#/PngImage/PngImage_Post

[xerikai]

Perfect, based on glyons I had put my sealed class swaggerformattribute inside the importfileparamtype class, after I looked at your checkin, I moved it out and everything started working. Thank you for the effort!

[RenanCarlosPereira]

senhores boa noite
achei uma solução que pode ajudar, neste caso abaixo, não depende de nomes de controles ou de actions, basta chamar na swagger e usar o IFormFile normalmente

using Microsoft.AspNetCore.Http;
using Swashbuckle.AspNetCore.Swagger;
using Swashbuckle.AspNetCore.SwaggerGen;
using System.Linq;

public class FileUploadOperation : IOperationFilter
{
    public void Apply(Operation operation, OperationFilterContext context)
    {
        if (operation.Parameters == null) return;

        var result = from a in context.ApiDescription.ParameterDescriptions
                     join b in operation.Parameters.OfType<NonBodyParameter>()
                     on a.Name equals b?.Name
                     where a.ModelMetadata.ModelType == typeof(IFormFile)
                     select b;


        result.ToList().ForEach(x =>
        {
            x.In = "formData";
            x.Description = "Upload file.";
            x.Type = "file";
        });
    }
}

a chamada fica assim

services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new Info { Title = "My API V1", Version = "v1" });
                c.OperationFilter<FileUploadOperation>();
            });

[theBoringCoder]

@RenanCarlosPereira your solution doesn't work when the IFormFile is tagged with [FromForm], but I've yet to figure out why. My knowledge of Swashbuckle is quite small.

[romipetrelis]

This is a bit hacky, @theBoringCoder , but it seems to be having the desired result when using [FromForm]. YMMV

public void Apply(Operation operation, OperationFilterContext context)
        {
            if (operation.Parameters == null) return;

            // if you don't use [Consumes("multipart/form-data")] on your operations, you don't need this
            if (!operation.Consumes.Contains("multipart/form-data")) return;

            var param = context.ApiDescription.ParameterDescriptions.FirstOrDefault(x =>
                x.ModelMetadata.ModelType == typeof(IFormFile));
            
            var existing = operation.Parameters.FirstOrDefault(x =>
                x.Name.Equals(param?.Name, StringComparison.InvariantCultureIgnoreCase));

            var toAdd = new NonBodyParameter
            {
                In = "formData",
                Type = "file",
                Description = existing?.Description,
                Name = existing?.Name ?? "file",
                Required = existing?.Required ?? false
            };

            if (existing != null) operation.Parameters.Remove(existing);
            
            operation.Parameters.Add(toAdd);
        }