The swagger adventures continue…
In .NET Core the current recommended way to upload a file in ASP.NET is with an IFormFile.
If you’re using an IFormFile in your ASP.NET Web Api like so:
[HttpPost("upload")]
public IActionResult UploadFile(IFormFile file)
{
N.B. Update December 2018. As of Swashbuckle 4.0, IFormFile is supported out of the box, so the filter below is no longer needed.
If you do this, the Swagger page as rendered by Swashbuckle won’t look correct:
However, if you install version 2.5.0 or later of my Swashbuckle.AspNetCore.Examples NuGet package, then you can add the [AddSwaggerFileUploadButton] attribute to your controller action, like so:
[HttpPost("upload")]
[AddSwaggerFileUploadButton]
public IActionResult UploadFile(IFormFile file)
{
and then enable my filter in your Startup.cs:
services.AddSwaggerGen(c =>
{
c.OperationFilter<AddFileParamTypesOperationFilter>();
Then you’ll get a nice upload button:
N.B. Update December 2018. As of Swashbuckle 4.0, IFormFile is supported out of the box, so the filter above is no longer needed.
Matt's work blog 
Above attribute expects parameter name to be “File” else it will fail to create the upload button. is there a way we can configure the parameter name ?
Please raise an issue on GitHub and I’ll look at it when I get a chance https://github.com/mattfrear/Swashbuckle.AspNetCore.Examples
I am not able to see the upload button but was doing the exact thing you mentioned. Any idea why? Thanks!
See Mahesh’s comment above – could that be your problem?
Can the IFormFile be one of many properties on a model object submitted in [FromBody]?
Dunno, I haven’t tried that. When I used it I was passing other parameters on the query string.
Thanks for responding Matt. Your Swashbuckle Examples package is just what the doctor ordered!
([FromForm]IFormFile file ,[FromForm]string otherParm) does work! The SwaggerUI however includes Headers, Dispositions, etc that clutter it up quite a bit.
When you leave [FromForm] off the file parameters, you get TWO “file” parameters in the SwaggerUI—one specified as “query” (the value of which doesn’t come through the method), and one from the body that has the upload button (thank you!!!!)–and this one DOES work.
I would love to be able to get the clean SwaggerUI with the upload button on the ONE parameter, without the Header, Dispositions etc or the superfluous duplicate “file” parameter.
Does this make sense? Please email me matt.page@niceincontact.com
Your work is much appreciated. Thank you so much!
Hi Matt,
I can’t say I’ve ever seen the [FromForm] attribute before.
Raise an issue on github at either https://github.com/mattfrear/Swashbuckle.Examples or https://github.com/mattfrear/Swashbuckle.AspNetCore.Examples depending on which version you’re using, and I’ll look at it when I get a chance (which won’t be any time soon).
I’m seeing the same thing as Matt here. Adding the [FromForm] attribute blows up the input form with discrete fields, and makes it fail. Leaving it off makes the form work, but with an extra field on it.
I wrote this in a couple of hours in 2017 when I had a specific use case for uploading a file to an API. I haven’t had to do that since, so I’m not going near the code until I do need to do that again.
It’s an open source library, so you’re welcome to tweak it and submit a PR :-)The latest version of the code lives here:
https://github.com/mattfrear/Swashbuckle.AspNetCore.Filters
It seems that as of Swashbuckle.AspNetCore 4.0, IFormFile is now supported out of the box, so my filter is no longer needed.