C# 如何将带有文件的实体作为表单数据从 HttpClient 发布到 API？

Question

I've got an ASP.NET Core API that receives an entity like this:

public class ChartDTO
{
    public string Name { get; set; }
    //public byte[] Image { get; set; }
    public IFormFile Image { get; set; }
}

The API controller is:

     [HttpPost]
    [Route("[action]")]
    public ActionResult Register([FromForm] ChartDTO dto) // Using IFormFile
    {
        if (dto.Image.Length > 0)
        {
            var filePath = Path.Combine("wwwroot\\Charts", dto.Name);
            using (var fileStream = new FileStream(filePath, FileMode.Create))
            {
                try
                {
                    dto.Image.CopyTo(fileStream);
                    return Ok(new { status = true, message = "Chart posted Successfully" });
                }
                catch (Exception)
                {
                    return BadRequest();
                }
            }
        }
        return BadRequest();
    }

It works great from Postman (Body = form-data, Name = "DEV.png", Image = the file), but I can not figure out how to replicate this in a console app. Found lots of similar question, but they all seem to focus on uploading a single file only and I need an entity. A Base64 byte array is an option for the image, but I couldn't get that to work either. Would strongly appreciate any help.

TIA! Dennis

Answer 1

Try this, it works fine for me. You have to define a MultipartFormDataContent

var requestContent = new MultipartFormDataContent(); 
var imageContent = new ByteArrayContent(ImageData);

requestContent.Add(imageContent, "image", "image.jpg");

await client.PostAsync(url, requestContent);

Answer 2

After some sleep I realized that further down the line in this project, I won't be able to use IFormFile as the image will have to be loaded and sent from MetaTrader 4. I therefore have to use a byte[] instead, which means the whole solution ends up being:

DTO:

public class ChartDTO
{
    public string Name { get; set; }
    public byte[] Image { get; set; }
}

Controller:

[HttpPost]
    [Route("[action]")]
    public ActionResult Register([FromBody] ChartDTO dto)
    {
        if (dto.Image.Length > 0)
        {
            string filePath = Path.Combine(env.WebRootPath + "\\Charts\\"+ dto.Name);
            try
            {
                using (FileStream binaryFileStream = new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite))
                {
                    binaryFileStream.Write(dto.Image, 0, dto.Image.Length);
                }
                return Ok();
            }
            catch (Exception)
            {
                return BadRequest();
            }
        }
        return BadRequest();
    }

App:

 public static void UploadScreenshot(string accountName)
    {
        //string url = "https://localhost:44369/api/Charts/Register";
        string url = LocalItems.baseURL + LocalItems.chartsURL;
        string fileName = accountName + ".png";
        var filePath = Path.Combine(LocalItems.DataFolder + "\\MQL4\\Files\\", fileName);

        if (File.Exists(filePath))
        {
            ChartDTO dto = new ChartDTO();
            dto.Name = fileName;
            dto.Image = File.ReadAllBytes(filePath);
            var json = JsonConvert.SerializeObject(dto);
            using (var client = new HttpClient())
            {
                // By calling .Result you are synchronously reading the result
                var response = client.PostAsync(url, new StringContent(json, Encoding.UTF8, "application/json")).Result;
            }
        }
    }

Sorry for wasting your time.

Re Dennis