Why file IFormFile = null?

Question

[Route("api/file")]
[Produces("application/json")]
[Consumes("application/json", "application/json-patch+json", "multipart/form-data")]
[ApiController]
public class FileController : ControllerBase
{
    public FileController()
    {
    }

    [HttpPost]
    public async Task<IActionResult> PostProfilePicture([FromQuery]IFormFile file)
    {
        var stream = file.OpenReadStream();
        var name = file.FileName;
        return null;
    }
}

Postman

Debug

In the end file = null How to solve this problem?

Answer 1

You are sending it as x-www-form-urlencoded. You have to send it as multipart/form-data. File uploads only possible in this mode, hence also IFormFile will be null on all other modes.

x-www-form-urlencoded is the default mode and only use for sending key/vale encoded pairs within the request body.

Also [FromQuery] isn't necessary, because you can't upload files via query parameters.

Answer 2

I guess you're getting null from IFormFile because you specify required attributes for this operation on the Controller class, not on the controller method. Updating your code as below will solve the problem.

[Route("api/file")]
[ApiController]
public class FileController : ControllerBase
{

    public FileController()
    {

    }

    [HttpPost]
    [Produces("application/json")]
    [Consumes("multipart/form-data")]
    public async Task<IActionResult> PostProfilePicture([FromForm]IFormFile file)
    {
        var stream = file.OpenReadStream();
        var name = file.FileName;
        return null;
    }
}

Hope this solves your problem.

Answer 3

You need to change attribute which selects source from which model binder will resolve IFormFile instance. Instead of [FromQuery] to [FromForm]:

public async Task<IActionResult> PostProfilePicture([FromForm]IFormFile file)