Adding Custom SOAP Headers in WCF 3.5

Programmatically adding custom headers to SOAP messages in Windows Communication Foundation enables advanced scenarios like routing, logging, and distributed tracing without modifying service contracts.

Use Cases for Custom Headers

Custom SOAP headers allow you to pass metadata and routing information separately from business data:

• Content-based routing: Route messages to different servers based on header values
• Correlation tracking: Pass correlation IDs for distributed tracing
• Multi-tenancy: Identify tenant context without polluting business logic

Implementation

Use OperationContextScope to add headers to outgoing messages:

ServicioFuncionarioClient sv = new ServicioFuncionarioClient();
using (new OperationContextScope(sv.InnerChannel))
{
    // Add local server routing header
    MessageHeader headerLocal = MessageHeader.CreateHeader(
        "Key",
        "http://serviciosproduccionCP",
        "HostCP");
    OperationContext.Current.OutgoingMessageHeaders.Add(headerLocal);

    // Add remote server routing header
    MessageHeader headerBogota = MessageHeader.CreateHeader(
        "Key",
        "http://serviciosproduccionBogota",
        "HostBogota");
    OperationContext.Current.OutgoingMessageHeaders.Add(headerBogota);

    // Make the service call with custom headers
    resultado = sv.FuncionarioLogin(login, passWord);
}

sv.Close();

Key Concepts

Important Notes

Modern Context

Note: While WCF 3.5 required programmatic header manipulation, modern protocols handle metadata differently. HTTP/2 and gRPC use native header mechanisms, GraphQL uses context objects, and REST APIs typically use HTTP headers directly. The fundamental concept of separating metadata from payload remains universal across all service architectures.