C#.NET WebApi返回各种类型(图片/json数据/字符串)，.net图片转二进制流或byte

using System.IO;  /// <summary>  /// WebApi返回图片  /// </summary>  public HttpResponseMessage GetQrCode()  {      var imgPath = @"D:\ITdosCom\Images\itdos.jpg";      //从图片中读取byte      var imgByte = File.ReadAllBytes(imgPath);      //从图片中读取流      var imgStream = new MemoryStream(File.ReadAllBytes(imgPath));      var resp = new HttpResponseMessage(HttpStatusCode.OK)      {          Content = new ByteArrayContent(imgByte)          //或者          //Content = new StreamContent(stream)      };      resp.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpg");      return resp;  }  /// <summary>  /// WebApi返回json数据  /// </summary>  public HttpResponseMessage GetQrCode()  {      var jsonStr = "{\"IsSuccess\":true,\"Data\":\"www.itdos.com\"}";      var result = new HttpResponseMessage(HttpStatusCode.OK)                      {                          Content = new StringContent(jsonStr, Encoding.UTF8, "text/json")                      };      return result;  }  /// <summary>  /// WebApi返回字符串  /// </summary>  public HttpResponseMessage GetQrCode()  {      var str = "IT大师www.itdos.com";      var result = new HttpResponseMessage(HttpStatusCode.OK)                      {                          Content = new StringContent(str, Encoding.UTF8, "text/plain")                      };      return result;  }