I’m writing an application which needs to host several WCF services. One of the strengths of WCF is the ability to configure services without having to recompile, by specifying settings in the app.config file.
When self-hosting, there does not appear to be an out-of-the-box way to automatically host services which are in the app.config file. I found this question which mentions a possible solution of dynamically enumerating services listed in app.config at runtime, and creating a ServiceHost for each.
However, my services, contracts, and the hosting application are all in different assemblies. This causes Type.GetType(string name) to fails to locate my service type (returns null) because it is defined in a different assembly.
How can I reliably host all services listed in the app.config file dynamically (i.e., without hard-coding new ServiceHost(typeof(MyService)) in my self-hosting application?
Note: My app.config was generated using the “WCF Configuration Editor” in Visual Studio 2010.
Note also: My primary goal is to have this driven by the app.config file so there is a single point of configuration. I don’t want to have to configure this in a separate location.
EDIT: I am able to read the app.config file (see here), but need to be able to resolve types in different assemblies.
EDIT: One of the answers below prompted me to try specifying the AssemblyQualifiedName in app.config instead of just the basic type name. This was able to get around the Type.GetType() problem, however ServiceHost.Open() now fails with an InvalidOperationException regardless of how I attain the type:
// Fails
string typeName = typeof(MyService).AssemblyQualifiedName;
Type myType = Type.GetType(typeName);
ServiceHost host = new ServiceHost(myType);
host.Open(); // throws InvalidOperationException
// Also fails
Type myType2 = typeof(MyService);
ServiceHost host2 = new ServiceHost(myType2);
host2.Open(); // throws InvalidOperationException
Exception details:
Service 'SO.Example.MyService' has zero application (non-infrastructure) endpoints. This might be because no configuration file was found for your application, or because no service element matching the service name could be found in the configuration file, or because no endpoints were defined in the service element.
I guess WCF attempts to match the literal string for the service name when parsing the app.config file internally.
EDIT/ANSWER: What I ended up doing was basically what was in the answer below. Instead of using Type.GetType() I know that all of my services are in the same assembly, so I switched to:
// Get a reference to the assembly which contain all of the service implementations.
Assembly implementationAssembly = Assembly.GetAssembly(typeof(MyService));
...
// When loading the type for the service, load it from the implementing assembly.
Type implementation = implementationAssembly.GetType(serviceElement.Name);
You correctly identified the answer to your problem in your question link and @marc_s answer also gives the correct approach too. The actual issue you are having is that you need to dynamically get the Type instance of an assembly that may only be referenced through a config file so it may not be loaded into the current AppDomain.
Look at this blog post for a way to dynamically reference assemblies in your code. Although the post is specifically for an ASP.NET application, the general approach should work in a self hosted scenario. The ideas is to replace the Type.GetType(string) call with a private method call that dynamically loads the requested assembly (if needed) and returns the Type object. The parameter you send this method will still be the element.Name and you’ll need to figure out which is the correct assembly to load. A simple convention-based assembly naming scheme should work. For example, if service type is:
then assume the assembly is: