Get the name of caller (or method) that created the WCF Service instance?

Question

as simple as i can:

i have a WCF service with a private constructor. if i'm not wrong, constructors must be parameterless in WCF and the parameter i need is the caller's name (or caller's method name), so i can assign a few readonly fields.

so, the question is: is there a way that i can get the caller's name -- or the method that invoked it? i was playing around with OperationContext.Current, but without any luck.

Answer 1

You can access the .NET call stack like this:

var trace = new System.Diagnostics.StackTrace();
var frame = trace.GetFrame( 1 ); // Frame 0 is current function
var callingMethodName = frame.GetMethod().Name;

I do not know whether this technique works in your situation, but you could give it a try.

Answer 2

I have never seen a valid case for the called method to do something different based on the identity of the caller. If the caller's identity matters, then the caller should pass into the called method whatever information it needs. Instead of:

public MyClass(string callerName) {
    if (callerName == "Caller1")
        _field = "Value1";
    else
        _field = "Value2";
}

use

public MyClass(string value) {
    _field = value;
}

Answer 3

I wouldn't recommend accessing the stack trace for performance reasons.

WCF service constructors only need to be parameterless if you are using the default ServiceHostFactory. You can specify a custom service factory in your .svc file like this:

<%@ ServiceHost Language="C#" Debug="true"
   Service="Namespace.To.Service"
   Factory="Namespace.To.ServiceFactory" %>

The process to creating your class in a custom way goes like this:

1. Your ServiceHostFactory creates an instance of your custom ServiceHost in CreateServiceHost
2. ServiceHost overrides OnOpening and adds a custom IServiceBehavior to Description.Behaviors (Description is a property on the base class)
3. Your IServiceBehavior implements ApplyDispatchBehavior and enumerates serviceHostBase.ChannelDispatchers, checking if each is a ChannelDispatcher.
   • Each ChannelDispatcher's Endpoints property is enumerated and it's DispatchRuntime.InstanceProvider is changed to a custom IInstanceProvider
4. The custom IInstanceProvider creates the instance in GetInstance

I have used this to delegate creation to an IoC container.

Answer 4

I think your best bet is to either break your service down to multiple similar services (yuk) or break out your method(s) to be overloads intended for different callers to use.

i.e. if you have Service1 which provides method foo() to CallerA and CallerB, maybe try making foo private, and exposing fooA() and fooB(), which are exclusively called by CallerA and CallerB, respectively. Then fooA() and fooB() can set the readonly properties appropriately before calling foo().