如何阻止WCF SOAP的WSDL随请求域名变更soapAction头？

WCF默认会根据请求的域名动态修改WSDL里的SOAP Action，导致不同域名访问时返回的soapAction和契约中定义的固定值不匹配，进而触发契约过滤不匹配的错误。以下是两种可行的解决办法：

方法一：自定义ServiceHost固定基地址 #

创建自定义ServiceHost，强制WSDL生成时使用契约中指定的固定域名作为基地址，这样soapAction就不会随请求域名变化。

代码示例：

public class FixedBaseAddressServiceHost : ServiceHost
{
    public FixedBaseAddressServiceHost(Type serviceType, params Uri[] baseAddresses) 
        : base(serviceType, baseAddresses) { }

    protected override void ApplyConfiguration()
    {
        base.ApplyConfiguration();
        // 替换为契约里的固定域名
        var fixedUri = new Uri("https://service-abc.com");
        BaseAddresses.Clear();
        BaseAddresses.Add(fixedUri);
    }
}

然后在Global.asax的Application_Start里用这个自定义Host启动服务：

protected void Application_Start(object sender, EventArgs e)
{
    using var host = new FixedBaseAddressServiceHost(typeof(YourServiceImplementation));
    host.Open();
}

方法二：自定义WsdlExporter替换soapAction #

通过自定义WsdlExporter，在WSDL生成过程中把所有动态生成的soapAction替换为契约中定义的固定值，适合需要保留多个基地址但固定soapAction的场景。

首先实现自定义WsdlExporter：

public class FixedActionWsdlExporter : WsdlExporter
{
    protected override void ExportEndpoint(ServiceEndpoint endpoint, XmlSchemaSet schemas)
    {
        base.ExportEndpoint(endpoint, schemas);

        // 遍历所有WSDL操作，替换soapAction为固定值
        foreach (var wsdlDoc in GeneratedWsdlDocuments)
        {
            foreach (var binding in wsdlDoc.Definitions.Bindings)
            {
                foreach (var operation in binding.Operations)
                {
                    var soapOp = operation.Extensions.Find<SoapOperationBinding>();
                    if (soapOp == null) continue;

                    // 根据操作名匹配替换，这里以GetTodos为例
                    switch (operation.Name)
                    {
                        case "GetTodos":
                            soapOp.SoapAction = "https://service-abc.com/GetTodos";
                            break;
                        // 其他操作照此添加
                        // case "AnotherOperation":
                        //     soapOp.SoapAction = "https://service-abc.com/AnotherOperation";
                        //     break;
                    }
                }
            }
        }
    }
}

接着创建对应的服务行为，让WCF使用这个自定义导出器：

public class FixedActionBehavior : IServiceBehavior
{
    public void AddBindingParameters(ServiceDescription desc, ServiceHostBase host, 
        Collection<ServiceEndpoint> endpoints, BindingParameterCollection parameters) { }

    public void ApplyDispatchBehavior(ServiceDescription desc, ServiceHostBase host) { }

    public void Validate(ServiceDescription desc, ServiceHostBase host)
    {
        var metadataBehavior = desc.Behaviors.Find<ServiceMetadataBehavior>();
        if (metadataBehavior != null)
        {
            metadataBehavior.MetadataExporter = new FixedActionWsdlExporter();
        }
    }
}

最后在代码里注册这个行为：

protected void Application_Start(object sender, EventArgs e)
{
    using var host = new ServiceHost(typeof(YourServiceImplementation));
    host.Description.Behaviors.Add(new FixedActionBehavior());
    host.Open();
}

验证 #

部署后用三个域名分别请求WSDL，检查<soap:operation>的soapAction是否均为https://service-abc.com/GetTodos，再用任意域名调用服务，确认不会再出现契约过滤不匹配的错误。

内容的提问来源于stack exchange，提问作者DavidGouge