/// <summary>
 /// 设置附件信息
 /// </summary>
 public static void SetAttachmentResult(string flag, byte[] result)
 {
     lock (AttachmentResults)
     {
         RemoveExpireResult();
         if (result == null)
         {
             AttachmentResults.Remove(flag);
         }
         else
         {
             AttachmentContent attachment = new AttachmentContent()
             {
                 Content  = result,
                 ExpireIn = DateTime.Now.AddDays(1)
             };
             AttachmentResults[flag] = attachment;
         }
     }
 }
 /// <summary>
 /// 获取附件信息
 /// </summary>
 /// <returns></returns>
 public static bool TryGetAttachmentResult(string flag, out byte[] result)
 {
     lock (AttachmentResults)
     {
         AttachmentContent attachment = null;
         if (AttachmentResults.TryGetValue(flag, out attachment))
         {
             if (attachment.ExpireIn < DateTime.Now)
             {
                 AttachmentResults.Remove(flag);
                 result = null;
                 return(false);
             }
             result = attachment.Content;
             return(true);
         }
     }
     result = null;
     return(false);
 }