C#: Posting Model from body and file as MultipartFormDataContent

问题

I'm looking for a way to send model and image in one request. I tried to send my model from body, but I don't know how to send the file. Is there another way than sending image and model in a different files?

Here's the POST method from my API:

[HttpPost]
[Route("UploadNewEvent")]
public async Task<IActionResult> CreateNewEventAsync([FromBody] EventModel model)
{
    var file = this.Request.Form.Files.LastOrDefault();

    if (file != null)
    {
        var uploads = Path.Combine(_environment.WebRootPath, "uploads");

        using (var fileStream = new FileStream(Path.Combine(uploads, "test.jpg"), FileMode.Create))
        {
            await file.CopyToAsync(fileStream);
        }
     }

     // do sth with model later    
     return Ok();
}

And here's the code from my App:

public async Task SendNewEvent(EventModel model, MediaFile photo)
{
    var uri = $"{baseUri}api/User/Event/CreateNewEvent";

    if (photo != null)
    {
        var multipartContent = new MultipartFormDataContent();
        multipartContent.Add(new StreamContent(photo.GetStream()), "\"file\"", $"\"{photo.Path}\"");

        var httpClient = new HttpClient();               
        var jsonObject = JsonConvert.SerializeObject(model);
        var stringContent = new StringContent(jsonObject, Encoding.UTF8, "application/json");
        var httpResponseMessage = await httpClient.PostAsync(uri, stringContent);
    }
}

回答1:

For passing Model with File parameter, you need to post data as form-data.

Follow steps below:

1. Change FromBody to FromForm

       [HttpPost]
   [Route("UploadNewEvent")]
   public async Task<IActionResult> CreateNewEventAsync([FromForm] EventModel model)
   {
       // do sth with model later    
       return Ok();
   }
   

2. Change client code to send form-data instead of json string

       var uri = $"https://localhost:44339/UploadNewEvent";
       FileStream fileStream = new FileStream(@"filepath\T1.PNG", FileMode.Open);
       var multipartContent = new MultipartFormDataContent();
       multipartContent.Add(new StreamContent(fileStream), "\"file\"", @"filepath\T1.PNG");
   
   
       // EventModel other fields
       multipartContent.Add(new StringContent("2"), "Id");
       multipartContent.Add(new StringContent("Tom"), "Name");
       var httpClient = new HttpClient();
       var httpResponseMessage = httpClient.PostAsync(uri, multipartContent).Result;
   

3. EventModel

   public class EventModel
   {
   public int Id { get; set; }
   public string Name { get; set; }
   public IFormFile File { get; set; }
   }
   

来源：https://stackoverflow.com/questions/52209852/c-posting-model-from-body-and-file-as-multipartformdatacontent