发布带有文件上传到 asp.net core api 的对象/键值

Question

I have been trying to post a file with additonal information to asp.net core 3+ post api. If I send these params individually, it works. However, I want to send the required information at once.

My Model in ASP.Net Core 3.1

public class PostItem
{
   public string Title { get; set; }
   public IFormFile File { get; set; }
}

The Post API

[HttpPost]
        public async Task<IActionResult> Post(PostItem item)
        {
            try
            {
                if (item == null)
                    return BadRequest();
                await Task.Delay(TimeSpan.FromMilliseconds(100));
                //Do Something here
                return Ok();
            }
            catch (Exception ex)
            {
                return StatusCode(500, ex.Message + "Internal server error");
            }
        }

Calling the API from Xamarin client

MultipartFormDataContent content = new MultipartFormDataContent();
var values = new[]
{
    new KeyValuePair<string, string>("Title", postItem.Title)
};
foreach(var keyValue in values)
{
      content.Add(new StringContent(keyValue.Value), keyValue.Key);
}

foreach (string file in imagePaths)
{
    byte[] byteArray = File.ReadAllBytes(file);
    content.Add(new ByteArrayContent(byteArray), "file", Path.GetFileName(file));
}
HttpClient client = new HttpClient();
var response = await client.PostAsync(Path.Combine(ApplicationConstants.apiUrl, "item/"), content);
//read response result as a string async into json var
var responsestr = response.Content.ReadAsStringAsync().Result;

I am getting 415 error Unsupported Media Type

The question is how to send the required parameter from Xamarin Client or how to include FileUpload as part of an object and send it to the api?

Answer 1

Decorate the input parameter in your post method with a [FromForm] tag to bind to the form.

public async Task<IActionResult> Post([FromForm] PostItem item)
{

}

This is assuming that your PostItem class matches the form you are posting. Adding [FromForm] should at least fix the 415.