Get all types implementing specific open generic type

Question

How do I get all types that implementing a specific open generic type?

For instance:

public interface IUserRepository : IRepository
         


        

Answer 1

Solution implemented without LINQ, searching both generic and non generic interfaces, filtering the return type to classes.

public static class SampleCode
{
    public static void Main()
    {
        IList loadableTypes;

        // instance the dummy class used to find the current assembly
        DummyClass dc = new DummyClass();

        loadableTypes = GetClassesImplementingAnInterface(dc.GetType().Assembly, typeof(IMsgXX)).Item2;
        foreach (var item in loadableTypes) {Console.WriteLine("1: " + item);}
        // print
        // 1: Start2.MessageHandlerXY

        loadableTypes = GetClassesImplementingAnInterface(dc.GetType().Assembly, typeof(IHandleMessageG<>)).Item2;
        foreach (var item in loadableTypes) { Console.WriteLine("2: " + item); }
        // print
        // 2: Start2.MessageHandlerXY
        // 2: Start2.MessageHandlerZZ
    }

    ///
Read all classes in an assembly that implement an interface (generic, or not generic)
    //
    // some references
    // return all types implementing an interface
    // http://stackoverflow.com/questions/26733/getting-all-types-that-implement-an-interface/12602220#12602220
    // http://haacked.com/archive/2012/07/23/get-all-types-in-an-assembly.aspx/
    // http://stackoverflow.com/questions/7889228/how-to-prevent-reflectiontypeloadexception-when-calling-assembly-gettypes
    // return all types implementing a generic interface
    // http://stackoverflow.com/questions/33694960/find-all-types-implementing-a-certain-generic-interface-with-specific-t-type
    // http://stackoverflow.com/questions/8645430/get-all-types-implementing-specific-open-generic-type
    // http://stackoverflow.com/questions/1121834/finding-out-if-a-type-implements-a-generic-interface
    // http://stackoverflow.com/questions/5849210/net-getting-all-implementations-of-a-generic-interface
    public static Tuple> GetClassesImplementingAnInterface(Assembly assemblyToScan, Type implementedInterface)
    {
        if (assemblyToScan == null)
            return Tuple.Create(false, (IList)null);

        if (implementedInterface == null || !implementedInterface.IsInterface)
            return Tuple.Create(false, (IList)null);

        IEnumerable typesInTheAssembly;

        try
        {
            typesInTheAssembly = assemblyToScan.GetTypes();
        }
        catch (ReflectionTypeLoadException e)
        {
            typesInTheAssembly = e.Types.Where(t => t != null);
        }

        IList classesImplementingInterface = new List();

        // if the interface is a generic interface
        if (implementedInterface.IsGenericType)
        {
            foreach (var typeInTheAssembly in typesInTheAssembly)
            {
                if (typeInTheAssembly.IsClass)
                {
                    var typeInterfaces = typeInTheAssembly.GetInterfaces();
                    foreach (var typeInterface in typeInterfaces)
                    {
                        if (typeInterface.IsGenericType)
                        {
                            var typeGenericInterface = typeInterface.GetGenericTypeDefinition();
                            var implementedGenericInterface = implementedInterface.GetGenericTypeDefinition();

                            if (typeGenericInterface == implementedGenericInterface)
                            {
                                classesImplementingInterface.Add(typeInTheAssembly);
                            }
                        }
                    }
                }
            }
        }
        else
        {
            foreach (var typeInTheAssembly in typesInTheAssembly)
            {
                if (typeInTheAssembly.IsClass)
                {
                    // if the interface is a non-generic interface
                    if (implementedInterface.IsAssignableFrom(typeInTheAssembly))
                    {
                        classesImplementingInterface.Add(typeInTheAssembly);
                    }
                }
            }
        }
        return Tuple.Create(true, classesImplementingInterface);
    }
}

public class DummyClass
{
}

public interface IHandleMessageG
{
}

public interface IHandleMessage
{
}

public interface IMsgXX
{
}

public interface IMsgXY
{
}

public interface IMsgZZ
{
}

public class MessageHandlerXY : IHandleMessageG, IHandleMessage, IMsgXX
{
    public string Handle(string a)
    {
        return "aaa";
    }
}

public class MessageHandlerZZ : IHandleMessageG, IHandleMessage
{
    public string Handle(string a)
    {
        return "bbb";
    }
}