Asp.Net Core swagger Help Pages for IFormFile

Question

I am trying to setup swagger for testing models which have IFormFile properties. For example I have next api method

[HttpPost]
public ApiResult<UserModel> SaveTestFileData([FromForm]TestPostFileArgs args)
{
    var result = new UserModel() { Id = 1, Name = $"SaveTestFileData {args.UserId} company: {args.CompanyId}, file length: {args.CompanyFile.Length}" };
    return ApiResult.Success(result);
}

And my parameter model

public class TestPostFileArgs
{
    public int UserId { get; set; }
    public int? CompanyId { get; set; }
    public IFormFile CompanyFile { get; set; }
}

By default swagger generate help page which does not allow to test it To solve this problem I wrote next OperationFilter

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

        var fileParamNames = context.ApiDescription.ActionDescriptor.Parameters
            .SelectMany(x => x.ParameterType.GetProperties())
            .Where(x => x.PropertyType.IsAssignableFrom(typeof (IFormFile)))
            .Select(x => x.Name)
            .ToList();
        if (!fileParamNames.Any())
            return;

        var paramsToRemove = new List<IParameter>();
        foreach (var param in operation.Parameters)
        {
            paramsToRemove.AddRange(from fileParamName in fileParamNames where param.Name.StartsWith(fileParamName + ".") select param);
        }
        paramsToRemove.ForEach(x => operation.Parameters.Remove(x));
        foreach (var paramName in fileParamNames)
        {
            var fileParam = new NonBodyParameter
                {
                    Type = "file",
                    Name = paramName,
                    In = "formData"
                };
            operation.Parameters.Add(fileParam);
        }
        foreach (IParameter param in operation.Parameters)
        {
            param.In = "formData";
        }

        operation.Consumes = new List<string>() { "multipart/form-data" };
    }
}

And after this everething works as I expect from swagger.

For now this solution works for me, but it feels not right. Maybe I am missing some simple solution for this. Also this approach does not handle List or complex object properties with IFormFile or maybe something else.

Answer 1

For you ASP.NET Core developers, there's an issue written up in the Swashbuckle.AspNetCore GitHub repo for this: https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/193. It has some working code for an OperationFilter in the comments as well -- that one worked better for me than the other ones in this question.