ASP.NET Web API upload image - asp.net

Question

How to upload an image using HttpWebRequest/WebRequest to server?
Server side action looks like this:
[HttpPost]
[Route("/uploadfile")]
public async Task<string> UploadFile([FromForm(Name = "fileName")] IFormFile image)
{
MemoryStream stream = new MemoryStream();
await image.CopyToAsync(stream);
...
}

Answer 1

According to the method of HttpWebRequest and your description, you can refer to the following code implementation.
Codes of Client in ASP.NET Core Console Application
static void Main(string[] args)
{
UploadFile("https://localhost:44391/uploadfile", "D:\\upload\\1.jpg", "image", "multipart/form-data;",new NameValueCollection { });
}
public static void UploadFile(string url, string file, string paramName, string contentType, NameValueCollection nvc)
{
string boundary = DateTime.Now.Ticks.ToString("x");
byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
//create request object
HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);
wr.ContentType = "multipart/form-data; boundary=" + boundary;
wr.Method = "POST";
wr.KeepAlive = true;
wr.Credentials = System.Net.CredentialCache.DefaultCredentials;
Stream rs = wr.GetRequestStream();
string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
foreach (string key in nvc.Keys)
{
rs.Write(boundarybytes, 0, boundarybytes.Length);
string formitem = string.Format(formdataTemplate, key, nvc[key]);
byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
rs.Write(formitembytes, 0, formitembytes.Length);
}
rs.Write(boundarybytes, 0, boundarybytes.Length);
string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
string header = string.Format(headerTemplate, paramName, file, contentType);
byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);
rs.Write(headerbytes, 0, headerbytes.Length);
//upload
FileStream fileStream = new FileStream(file, FileMode.Open, FileAccess.Read);
byte[] buffer = new byte[4096];
int bytesRead = 0;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
{
rs.Write(buffer, 0, bytesRead);
}
fileStream.Close();
byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
rs.Write(trailer, 0, trailer.Length);
rs.Close();
WebResponse wresp = null;
try
{
wresp = wr.GetResponse();
Stream stream2 = wresp.GetResponseStream();
StreamReader reader2 = new StreamReader(stream2);
Console.WriteLine(string.Format("File uploaded, server response is: {0}", reader2.ReadToEnd()));
}
catch (Exception ex)
{
Console.WriteLine("Error uploading file", ex);
if (wresp != null)
{
wresp.Close();
wresp = null;
}
}
finally
{
wr = null;
}
}
Controller codes of server
[HttpPost]
[Route("/uploadfile")]
public async Task<string> UploadFile([FromForm(Name ="image")] IFormFile image)
{
if (image == null) return "is null";
Console.WriteLine(image.FileName);
Console.WriteLine(image.Length);
MemoryStream stream = new MemoryStream();
await image.CopyToAsync(stream);
return "true";
}
Screenshots of test