Hi, Some times we need to upload files on a web server using HttpWebRequest.

For that first we need to define a model (class) that represents the uploaded file property.

public class UploadFile
{       
   public string Name { get; set; }
   public string Filename { get; set; }
   public string ContentType { get; set; }
   public Stream Stream { get; set; }
}

Use below sample code for uploading files using httpWebRequest.

public byte[] UploadFilesToServer(string address, IEnumerable files, NameValueCollection values)
    {
        var request = WebRequest.Create(address);
        request.Method = "POST";
        var boundary = "---------------------------" + DateTime.Now.ToString("a", NumberFormatInfo.InvariantInfo);
        request.ContentType = "multipart/form-data; boundary=" + boundary;
        boundary = "--" + boundary;

        using (var requestStream = request.GetRequestStream())
        {
            // Write the values
            foreach (string name in values.Keys)
            {
                var buffer = Encoding.ASCII.GetBytes(boundary + Environment.NewLine);
                requestStream.Write(buffer, 0, buffer.Length);
                buffer = Encoding.ASCII.GetBytes(string.Format("Content-Disposition: form-data; name=\"{0}\"{1}{1}", name, Environment.NewLine));
                requestStream.Write(buffer, 0, buffer.Length);
                buffer = Encoding.UTF8.GetBytes(values[name] + Environment.NewLine);
                requestStream.Write(buffer, 0, buffer.Length);
            }

            // Write the files
            foreach (var file in files)
            {
                var buffer = Encoding.ASCII.GetBytes(boundary + Environment.NewLine);
                requestStream.Write(buffer, 0, buffer.Length);
                buffer = Encoding.UTF8.GetBytes(string.Format("Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"{2}", file.Name, file.Filename, Environment.NewLine));
                requestStream.Write(buffer, 0, buffer.Length);
                buffer = Encoding.ASCII.GetBytes(string.Format("Content-Type: {0}{1}{1}", file.ContentType, Environment.NewLine));
                requestStream.Write(buffer, 0, buffer.Length);
                file.Stream.CopyTo(requestStream);
                buffer = Encoding.ASCII.GetBytes(Environment.NewLine);
                requestStream.Write(buffer, 0, buffer.Length);
            }

            var boundaryBuffer = Encoding.ASCII.GetBytes(boundary + "--");
            requestStream.Write(boundaryBuffer, 0, boundaryBuffer.Length);
        }

        using (var response = request.GetResponse())
        using (var responseStream = response.GetResponseStream())
        using (var stream = new MemoryStream())
        {
            responseStream.CopyTo(stream);
            return stream.ToArray();
        }
    }