Reflect A Class, Reproduce Methods in Interface And Implemented Class?

Question

I am using WCF, and it uses interfaces, operation contracts, and all that jazz to expose the relevant methods.

However, what if one assumes that a separate class contains all the methods, and rather than have to basically write the same method signature on the interface/class that implements said interface, it uses some voodoo to automagically make these available in the interface/class. For example, consider the following:

[ServiceContract]    
public interface IService {

    [OperationContract]
    List<Foo> SelectAllFoo(string id);    
}    

public class Service : IService {

    public List<Foo> SelectAllFoo(string id)
    {
        // this just calls same method from Helpers class, same sig    
        return Helpers.SelectAllFoo(id);
    }    
}

I have like 500 methods I have to expose to the service, and it would be a lot of typing to put them in the service. So, in essence, I was hoping there might be a way to pass a class(es), return all the methods, and "inject" them more or less into the interface/class.

See if you can do what you need with [impromptu-interface](https://github.com/ekonbenefits/impromptu-interface) — Tim S., Dec 06 '13 at 22:10
It looks like that will require me to have the all methods on the interface, no? — user3010406, Dec 06 '13 at 22:15
If you are using a tool like CodeRush or Resharper, you could use the Extract Interface refactoring on the class and it would create the interface from the class, but you would still have to add the attributes (which you might be able to automate) — Rick Hodder, Dec 06 '13 at 22:23
I was thinking of someway to exploit reflection so it took care of everything. — user3010406, Dec 06 '13 at 22:24
this is similar: http://stackoverflow.com/questions/17120688/adding-servicecontract-operationcontract-at-runtime however unanswered. — user3010406, Dec 06 '13 at 22:31
Maybe you could use T4 templates to generate the interface and class based on the other class? — Tim S., Dec 06 '13 at 23:16
500 methods? Have you considered that maybe your architecture needs some reworking? — Daniel Mann, Dec 06 '13 at 23:30
This might be helpful for you https://stackoverflow.com/a/49160189/3057246 — Vinod Srivastav, Feb 25 '19 at 05:03

Konrad Kokosa · Accepted Answer · 2013-12-07T08:13:24.057

It is possible to solve you problem with usage of Reflection:

a) Use Reflection to enumerate all public methods from classes of your interests, for example:

var methods = typeof(SomeClass).GetMethods(BindingFlags.Instance | BindingFlags.Public);

b) Use this list to generate a source code for your service into a string

StringBuilder source = new StringBuilder();
source.AppendLine("using System;");
source.AppendLine("using System.ServiceModel;");
source.AppendLine("[ServiceContract]");
source.AppendLine("public class DynamicService {");
// Here for each MethodInfo from list generate a method source like
foreach (var method in methods)
{
    if (method.ReturnType == typeof(void))
        continue;
    string parameters = string.Join(", ", method.GetParameters().Select(pi => string.Format("{0} {1}", pi.ParameterType.Name, pi.Name)));
    string arguments = string.Join(", ", method.GetParameters().Select(pi => pi.Name));
    source.AppendFormat("[OperationContract]");
    source.AppendFormat("public {0} {1}({2})", method.ReturnType.Name, method.Name, parameters);
    source.AppendFormat("{{   return ConsoleApplication.Helpers.{0}({1}); }}", method.Name, arguments);
}
source.AppendLine("}");

Note: You will need some filtering here, for example to filter out ToString etc. As a example I bypass all void methods.

c) use CSharpCodeProvider to compile service source:

CSharpCodeProvider codeProvider = new CSharpCodeProvider();
System.CodeDom.Compiler.CompilerParameters param = new CompilerParameters();
param.GenerateExecutable = false;
param.GenerateInMemory = true;
param.ReferencedAssemblies.Add("System.Runtime.Serialization.dll");
param.ReferencedAssemblies.Add("System.ServiceModel.dll");
param.ReferencedAssemblies.Add("System.dll");
param.ReferencedAssemblies.Add("ConsoleApplication.exe");
CompilerResults result = codeProvider.CompileAssemblyFromSource(param, source.ToString());

Note: Here you can add reference to assemblies containing your helper classes, ConsoleApplication.exe in my example.

d) use your dynamic service as a normal one. For example you can self-host it:

if (!result.Errors.HasErrors)
{
    Type type = result.CompiledAssembly.GetType("DynamicService");
    var instance = Activator.CreateInstance(type);

    Uri baseAddress = new Uri("http://localhost:80/hello");
    using (ServiceHost host = new ServiceHost(type, baseAddress))
    {
        ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
        smb.HttpGetEnabled = true;
        smb.MetadataExporter.PolicyVersion = PolicyVersion.Policy15;
        host.Description.Behaviors.Add(smb);

        host.Open();

        Console.WriteLine("The service is ready at {0}", baseAddress);
        Console.WriteLine("Press <Enter> to stop the service.");
        Console.ReadLine();

        // Close the ServiceHost.
        host.Close();
    }
}

e) and then you have it:

enter image description here

f) if you want to host this service in IIS, you will have to provide your own custom ServiceHostFactory

tyvm! Very awesome explanation. – user3010406 Dec 07 '13 at 16:28 — user3010406, Dec 07 '13 at 16:28

Reflect A Class, Reproduce Methods in Interface And Implemented Class?

1 Answers1