Web API 自定义文件内容的定制类

    public class FileContent : HttpContent
    {
        private readonly Stream _stream;

        public FileContent(string path, string mediaType = "application/octet-stream")
        {
            _stream = new FileStream(path, FileMode.Open, FileAccess.Read);
            Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(mediaType);
        }


        protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
        {
            return _stream.CopyToAsync(stream);
        }

        protected override bool TryComputeLength(out long length)
        {
            if (_stream.CanSeek)
            {
                length = _stream.Length;
                return true;
            }

            length = 0;
            return false;
        }

        protected override void Dispose(bool disposing)
        {
            _stream.Dispose();
        }
    }

调用

            string path = @"H:各类知识练习MyWebApiWebApiImg1.jpg";
            var response = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new FileContent(path) //默认提示下载
                //Content = new FileContent(path,"image/jpg") //直接显示图片
            };
            return response;