C# Upload imagen FromForm , Multipart

class.cs

public class FIleUploadAPI
{
    public IFormFile oneimage { get; set; }
    public String cellNumber { get; set; }
    public String otroCampo { get; set; }
    public String otroCampo2 { get; set; }
}

[Route("/api/v1/student/CAU/Ticket/new")]
[HttpPost]
public String postre([FromForm] FIleUploadAPI formdata)
{
    if (!ModelState.IsValid)
    {
        return "Unsuccessful";
    }

    if (formdata.oneimage.Length > 0)
    {
        try
        {
            if (!Directory.Exists("/Users/plaga/Documents/dev/media"))
            {
                Directory.CreateDirectory("/Users/plaga/Documents/dev/media");
            }
            using (FileStream filestream = System.IO.File.Create("/Users/plaga/Documents/dev/media/" + formdata.oneimage.FileName))
            {
                formdata.oneimage.CopyTo(filestream);
                filestream.Flush();
                return "/Users/plaga/Documents/dev/media/" + formdata.oneimage.FileName;
            }
        }
        catch (Exception ex)
        {
            return ex.ToString();
        }
    }
    else
    {
        return "Unsuccessful";
    }
}