当消息是死信时，消息连同死信的原因和错误描述一起被移动到死信队列。dead-letter reason和error description被添加到消息属性中。
谢谢@Sean Feldman的评论。
您需要安装NuGet Azure.Messaging.ServiceBus -Version 7.13.1

我尝试了下面的方法，并能够读取属性。
插入消息到服务总线队列，并读取消息，并使用以下代码将其移动到死信队列。

读取消息的示例代码。

string connSB = "Connection";
string que = "myqueue11";
string Remove_msg = "Hello";  
QueueClient Qclnt = new QueueClient(connSB, que);
MessageReceiver msgRcvr = new MessageReceiver(connSB, que, ReceiveMode.PeekLock);
        while (true)
        {
            Message message = await msgRcvr.ReceiveAsync();
            if (message == null || message.Body == null || message.Body.Length == 0)
            {
                break;
            }
            string messageContent = Encoding.UTF8.GetString(message.Body);
            if ((messageContent.Contains(Remove_msg)))
            {
                await msgRcvr.AbandonAsync(message.SystemProperties.LockToken);
                Console.WriteLine($"Item '{Remove_msg}' not found.");
            }
        }

        await Qclnt.CloseAsync();
        await msgRcvr.CloseAsync();

用C#编写代码以读取属性。

string connSB = @"Conn String";
string queue = "myqueue11";
ServiceBusClient clnt = new ServiceBusClient(connSB);
ServiceBusReceiver receiver = clnt.CreateReceiver(queue, new ServiceBusReceiverOptions
            {
                    SubQueue = SubQueue.DeadLetter
            });
            ServiceBusReceivedMessage msg = await receiver.ReceiveMessageAsync();
            if (msg == null)
            {
                    Console.WriteLine("No messages available in the dead-letter queue.");
            }

     else
        {
            if (msg.ApplicationProperties.Count > 0)
              {
                 foreach (KeyValuePair<string, object> prop in msg.ApplicationProperties)
                  {
                      Console.WriteLine($"Key: {prop.Key}, Value: {prop.Value}");
                  }
                }
             else
              {
                  Console.WriteLine("No ApplicationProperties found for the message.");
               }
                await receiver.CloseAsync();
                await clnt.DisposeAsync();
          }

死信队列属性。