问题描述

在 C# Azure Function使用 Service Bus 作为触发器时候，在C# 独立工作模式下，说可以支持使用 ServiceBusReceivedMessage 类型作为触发消息的参数类型：

        [Function(nameof(ServiceBusReceivedMessageFunction))]
        [ServiceBusOutput("outputQueue", Connection = "ServiceBusConnection")]
        public string ServiceBusReceivedMessageFunction(
            [ServiceBusTrigger("queue", Connection = "ServiceBusConnection")] ServiceBusReceivedMessage message)
        {
            _logger.LogInformation("Message ID: {id}", message.MessageId);
            _logger.LogInformation("Message Body: {body}", message.Body);
            _logger.LogInformation("Message Content-Type: {contentType}", message.ContentType);

            var outputMessage = $"Output message created at {DateTime.Now}";
            return outputMessage;
        }

但是在实际的测试中，却报错： 

Cannot convert input parameter 'message' to type 'Azure.Messaging.ServiceBus.ServiceBusReceivedMessage' from type 'System.String'.

Error:System.NotSupportedException:

Deserialization of types without a parameterless constructor, a singular parameterized constructor, or a parameterized constructor annotated with 'JsonConstructorAttribute' is not supported.

Type 'Azure.Messaging.ServiceBus.ServiceBusReceivedMessage'.

Path: $ | LineNumber: 0 | BytePositionInLine: 1.

问题解答

这是 Azure Functions 基础结构的限制而导致的行为。由于ServiceBusReceivedMessage 类型无法反序列化为JSON 类型.

所以，可以使用 [string message] 来代替 [ServiceBusReceivedMessage message].

        [Function(nameof(ServiceBusReceivedMessageFunction))]
        [ServiceBusOutput("outputQueue", Connection = "ServiceBusConnection")]
        public string ServiceBusReceivedMessageFunction(
            [ServiceBusTrigger("queue", Connection = "ServiceBusConnection")] string message)
        {
            _logger.LogInformation("Message Body: {body}", message);

            var outputMessage = $"Output message created at {DateTime.Now}";
            return outputMessage;
        }

参考资料

Azure Functions 的 Azure 服务总线触发器 : https://docs.azure.cn/zh-cn/azure-functions/functions-bindings-service-bus-trigger?tabs=python-v2%2Cisolated-process%2Cnodejs-v4%2Cextensionv5&pivots=programming-language-csharp#usage

ServiceBusMessageActions raises grpc exception after migrating to Isolated worker in net8.0 in servicebus trigger execution #2761 ： https://github.com/Azure/azure-functions-dotnet-worker/issues/2761