.NET应用添加SOAP头Transaction ID及Polly重试协同问题

针对你遇到的Polly与IClientMessageInspector互不感知的问题，以下是几种实用的解决思路，均无需依赖外部工具，纯代码实现：

方案一：利用Polly Context传递Transaction ID #

核心思路是把首次生成的Transaction ID存入Polly的上下文对象，重试时从上下文读取复用，而非每次生成新ID。

步骤与代码示例 #

1. 扩展自动生成的SOAP客户端，添加Polly Context的存储属性：

public partial class YourSoapClient : ClientBase<IYourSoapService>, IYourSoapService
{
    // 用于存储Polly上下文
    public Context PollyContext { get; set; }
    // 保留VS自动生成的其他代码
}

2. 实现带上下文感知的IClientMessageInspector：

public class TransactionIdInspector : IClientMessageInspector
{
    public object BeforeSendRequest(ref Message request, IClientChannel channel)
    {
        var soapClient = channel as YourSoapClient;
        if (soapClient?.PollyContext != null)
        {
            // 上下文无ID则生成，有则直接复用
            if (!soapClient.PollyContext.TryGetValue("TransactionId", out var idObj))
            {
                var transactionId = Guid.NewGuid().ToString();
                soapClient.PollyContext["TransactionId"] = transactionId;
                AddTransactionHeader(ref request, transactionId);
            }
            else
            {
                AddTransactionHeader(ref request, idObj.ToString());
            }
        }
        else
        {
            // 无Polly上下文时，生成新ID（非重试场景）
            AddTransactionHeader(ref request, Guid.NewGuid().ToString());
        }
        return null;
    }

    private void AddTransactionHeader(ref Message request, string transactionId)
    {
        // 构造SOAP头并添加到请求中，替换为你的服务命名空间
        var header = new MessageHeader<string>(transactionId);
        var untypedHeader = header.GetUntypedHeader("TransactionId", "http://your-service-namespace");
        request.Headers.Add(untypedHeader);
    }

    public void AfterReceiveReply(ref Message reply, object correlationState) { }
}

3. Polly重试策略与客户端结合使用：

// 定义重试策略（根据实际失败类型调整异常捕获）
var retryPolicy = Policy
    .Handle<SoapException>()
    .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));

// 发起请求时绑定上下文
using var client = new YourSoapClient();
var pollyContext = new Context();
client.PollyContext = pollyContext;

// 确保Inspector已添加到客户端行为
client.Endpoint.Behaviors.Add(new TransactionIdInspector());

await retryPolicy.ExecuteAsync(ctx => client.TargetSoapMethodAsync(), pollyContext);

方案二：绕过Inspector，直接在Polly逻辑中复用Transaction ID #

如果不想依赖IClientMessageInspector，可以直接在Polly的执行委托中手动设置SOAP头，确保重试时使用同一个ID。

代码示例 #

// 首次生成唯一Transaction ID
var fixedTransactionId = Guid.NewGuid().ToString();

var retryPolicy = Policy
    .Handle<SoapException>()
    .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));

using var client = new YourSoapClient();
await retryPolicy.ExecuteAsync(async () =>
{
    // 每次请求前重置SOAP头（避免重复添加）
    client.InnerChannel.OperationContext.OutgoingMessageHeaders.RemoveAll("TransactionId", "http://your-service-namespace");
    
    // 手动添加固定的Transaction ID头
    var header = new MessageHeader<string>(fixedTransactionId);
    var untypedHeader = header.GetUntypedHeader("TransactionId", "http://your-service-namespace");
    client.InnerChannel.OperationContext.OutgoingMessageHeaders.Add(untypedHeader);
    
    // 调用SOAP接口
    return await client.TargetSoapMethodAsync();
});

方案三：在客户端实例级别存储Transaction ID #

扩展SOAP客户端，让每个客户端实例对应一个固定的Transaction ID，重试时复用同一个客户端实例即可。

代码示例 #

public partial class YourSoapClient
{
    // 每个客户端实例对应唯一的Transaction ID
    public string TransactionId { get; } = Guid.NewGuid().ToString();

    public YourSoapClient() : base()
    {
        // 自动添加自定义Behavior
        this.Endpoint.Behaviors.Add(new TransactionIdBehavior(this));
    }

    private class TransactionIdBehavior : IEndpointBehavior
    {
        private readonly YourSoapClient _client;

        public TransactionIdBehavior(YourSoapClient client)
        {
            _client = client;
        }

        public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) { }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
        {
            // 添加绑定当前实例ID的Inspector
            clientRuntime.MessageInspectors.Add(new TransactionIdInspector(_client.TransactionId));
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher) { }

        public void Validate(ServiceEndpoint endpoint) { }
    }

    private class TransactionIdInspector : IClientMessageInspector
    {
        private readonly string _fixedTransactionId;

        public TransactionIdInspector(string transactionId)
        {
            _fixedTransactionId = transactionId;
        }

        public object BeforeSendRequest(ref Message request, IClientChannel channel)
        {
            var header = new MessageHeader<string>(_fixedTransactionId);
            var untypedHeader = header.GetUntypedHeader("TransactionId", "http://your-service-namespace");
            request.Headers.Add(untypedHeader);
            return null;
        }

        public void AfterReceiveReply(ref Message reply, object correlationState) { }
    }
}

使用时只需复用同一个客户端实例，Polly重试时自然会使用同一个Transaction ID：

using var client = new YourSoapClient();
var retryPolicy = Policy
    .Handle<SoapException>()
    .WaitAndRetryAsync(3, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));

await retryPolicy.ExecuteAsync(() => client.TargetSoapMethodAsync());

关于Visual Studio配置的说明 #

无法通过Visual Studio的WSDL生成工具（添加服务引用/SvcUtil）直接配置实现这种逻辑。VS生成的仅为基础的SOAP客户端代码，自定义的重试与Transaction ID绑定逻辑必须通过手动编码扩展实现。

内容的提问来源于stack exchange，提问作者user2727133