Check if a class is derived from a generic class

Question

I have a generic class in my project with derived classes.

public class GenericClass : GenericInterface
{
}

public class Test : GenericCla         


        

Answer 1

It seems to me that this implementation works in more cases (generic class and interface with or without initiated parameters, regardless of the number of child and parameters):

public static class ReflexionExtension
{
    public static bool IsSubClassOfGeneric(this Type child, Type parent)
    {
        if (child == parent)
            return false;

        if (child.IsSubclassOf(parent))
            return true;

        var parameters = parent.GetGenericArguments();
        var isParameterLessGeneric = !(parameters != null && parameters.Length > 0 &&
            ((parameters[0].Attributes & TypeAttributes.BeforeFieldInit) == TypeAttributes.BeforeFieldInit));

        while (child != null && child != typeof(object))
        {
            var cur = GetFullTypeDefinition(child);
            if (parent == cur || (isParameterLessGeneric && cur.GetInterfaces().Select(i => GetFullTypeDefinition(i)).Contains(GetFullTypeDefinition(parent))))
                return true;
            else if (!isParameterLessGeneric)
                if (GetFullTypeDefinition(parent) == cur && !cur.IsInterface)
                {
                    if (VerifyGenericArguments(GetFullTypeDefinition(parent), cur))
                        if (VerifyGenericArguments(parent, child))
                            return true;
                }
                else
                    foreach (var item in child.GetInterfaces().Where(i => GetFullTypeDefinition(parent) == GetFullTypeDefinition(i)))
                        if (VerifyGenericArguments(parent, item))
                            return true;

            child = child.BaseType;
        }

        return false;
    }

    private static Type GetFullTypeDefinition(Type type)
    {
        return type.IsGenericType ? type.GetGenericTypeDefinition() : type;
    }

    private static bool VerifyGenericArguments(Type parent, Type child)
    {
        Type[] childArguments = child.GetGenericArguments();
        Type[] parentArguments = parent.GetGenericArguments();
        if (childArguments.Length == parentArguments.Length)
            for (int i = 0; i < childArguments.Length; i++)
                if (childArguments[i].Assembly != parentArguments[i].Assembly || childArguments[i].Name != parentArguments[i].Name || childArguments[i].Namespace != parentArguments[i].Namespace)
                    if (!childArguments[i].IsSubclassOf(parentArguments[i]))
                        return false;

        return true;
    }
}

Here are my 70 76 test cases:

[TestMethod]
public void IsSubClassOfGenericTest()
{
    Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(BaseGeneric<>)), " 1");
    Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(WrongBaseGeneric<>)), " 2");
    Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), " 3");
    Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IWrongBaseGeneric<>)), " 4");
    Assert.IsTrue(typeof(IChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), " 5");
    Assert.IsFalse(typeof(IWrongBaseGeneric<>).IsSubClassOfGeneric(typeof(ChildGeneric2<>)), " 6");
    Assert.IsTrue(typeof(ChildGeneric2<>).IsSubClassOfGeneric(typeof(BaseGeneric<>)), " 7");
    Assert.IsTrue(typeof(ChildGeneric2).IsSubClassOfGeneric(typeof(BaseGeneric<>)), " 8");
    Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(BaseGeneric)), " 9");
    Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(WrongBaseGeneric)), "10");
    Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric)), "11");
    Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IWrongBaseGeneric)), "12");
    Assert.IsTrue(typeof(IChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric)), "13");
    Assert.IsFalse(typeof(BaseGeneric).IsSubClassOfGeneric(typeof(ChildGeneric2)), "14");
    Assert.IsTrue(typeof(ChildGeneric2).IsSubClassOfGeneric(typeof(BaseGeneric)), "15");
    Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(ChildGeneric)), "16");
    Assert.IsFalse(typeof(IChildGeneric).IsSubClassOfGeneric(typeof(IChildGeneric)), "17");
    Assert.IsFalse(typeof(IBaseGeneric<>).IsSubClassOfGeneric(typeof(IChildGeneric2<>)), "18");
    Assert.IsTrue(typeof(IChildGeneric2<>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "19");
    Assert.IsTrue(typeof(IChildGeneric2).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "20");
    Assert.IsFalse(typeof(IBaseGeneric).IsSubClassOfGeneric(typeof(IChildGeneric2)), "21");
    Assert.IsTrue(typeof(IChildGeneric2).IsSubClassOfGeneric(typeof(IBaseGeneric)), "22");
    Assert.IsFalse(typeof(IBaseGeneric).IsSubClassOfGeneric(typeof(BaseGeneric)), "23");
    Assert.IsTrue(typeof(BaseGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric)), "24");
    Assert.IsFalse(typeof(IBaseGeneric<>).IsSubClassOfGeneric(typeof(BaseGeneric<>)), "25");
    Assert.IsTrue(typeof(BaseGeneric<>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "26");
    Assert.IsTrue(typeof(BaseGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "27");
    Assert.IsFalse(typeof(IBaseGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric)), "28");
    Assert.IsTrue(typeof(BaseGeneric2).IsSubClassOfGeneric(typeof(IBaseGeneric)), "29");
    Assert.IsFalse(typeof(IBaseGeneric<>).IsSubClassOfGeneric(typeof(BaseGeneric2<>)), "30");
    Assert.IsTrue(typeof(BaseGeneric2<>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "31");
    Assert.IsTrue(typeof(BaseGeneric2).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "32");
    Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "33");
    Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(WrongBaseGenericA<,>)), "34");
    Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "35");
    Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IWrongBaseGenericA<,>)), "36");
    Assert.IsTrue(typeof(IChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "37");
    Assert.IsFalse(typeof(IWrongBaseGenericA<,>).IsSubClassOfGeneric(typeof(ChildGenericA2<,>)), "38");
    Assert.IsTrue(typeof(ChildGenericA2<,>).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "39");
    Assert.IsTrue(typeof(ChildGenericA2).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "40");
    Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(BaseGenericA)), "41");
    Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(WrongBaseGenericA)), "42");
    Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA)), "43");
    Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IWrongBaseGenericA)), "44");
    Assert.IsTrue(typeof(IChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA)), "45");
    Assert.IsFalse(typeof(BaseGenericA).IsSubClassOfGeneric(typeof(ChildGenericA2)), "46");
    Assert.IsTrue(typeof(ChildGenericA2).IsSubClassOfGeneric(typeof(BaseGenericA)), "47");
    Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(ChildGenericA)), "48");
    Assert.IsFalse(typeof(IChildGenericA).IsSubClassOfGeneric(typeof(IChildGenericA)), "49");
    Assert.IsFalse(typeof(IBaseGenericA<,>).IsSubClassOfGeneric(typeof(IChildGenericA2<,>)), "50");
    Assert.IsTrue(typeof(IChildGenericA2<,>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "51");
    Assert.IsTrue(typeof(IChildGenericA2).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "52");
    Assert.IsFalse(typeof(IBaseGenericA).IsSubClassOfGeneric(typeof(IChildGenericA2)), "53");
    Assert.IsTrue(typeof(IChildGenericA2).IsSubClassOfGeneric(typeof(IBaseGenericA)), "54");
    Assert.IsFalse(typeof(IBaseGenericA).IsSubClassOfGeneric(typeof(BaseGenericA)), "55");
    Assert.IsTrue(typeof(BaseGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA)), "56");
    Assert.IsFalse(typeof(IBaseGenericA<,>).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "57");
    Assert.IsTrue(typeof(BaseGenericA<,>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "58");
    Assert.IsTrue(typeof(BaseGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "59");
    Assert.IsFalse(typeof(IBaseGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA)), "60");
    Assert.IsTrue(typeof(BaseGenericA2).IsSubClassOfGeneric(typeof(IBaseGenericA)), "61");
    Assert.IsFalse(typeof(IBaseGenericA<,>).IsSubClassOfGeneric(typeof(BaseGenericA2<,>)), "62");
    Assert.IsTrue(typeof(BaseGenericA2<,>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "63");
    Assert.IsTrue(typeof(BaseGenericA2).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "64");
    Assert.IsFalse(typeof(BaseGenericA2).IsSubClassOfGeneric(typeof(IBaseGenericA)), "65");
    Assert.IsFalse(typeof(BaseGenericA).IsSubClassOfGeneric(typeof(ChildGenericA2)), "66");
    Assert.IsFalse(typeof(BaseGenericA2).IsSubClassOfGeneric(typeof(BaseGenericA)), "67");
    Assert.IsTrue(typeof(ChildGenericA3).IsSubClassOfGeneric(typeof(BaseGenericB)), "68");
    Assert.IsTrue(typeof(ChildGenericA4).IsSubClassOfGeneric(typeof(IBaseGenericB)), "69");
    Assert.IsFalse(typeof(ChildGenericA3).IsSubClassOfGeneric(typeof(BaseGenericB)), "68-2");
    Assert.IsTrue(typeof(ChildGenericA3).IsSubClassOfGeneric(typeof(BaseGenericB)), "68-3");
    Assert.IsFalse(typeof(ChildGenericA3).IsSubClassOfGeneric(typeof(BaseGenericB)), "68-4");
    Assert.IsFalse(typeof(ChildGenericA4).IsSubClassOfGeneric(typeof(IBaseGenericB)), "69-2");
    Assert.IsTrue(typeof(ChildGenericA4).IsSubClassOfGeneric(typeof(IBaseGenericB)), "69-3");
    Assert.IsFalse(typeof(ChildGenericA4).IsSubClassOfGeneric(typeof(IBaseGenericB)), "69-4");
    Assert.IsFalse(typeof(bool).IsSubClassOfGeneric(typeof(IBaseGenericB)), "70");
}

Classes and interfaces for testing :

public class Class1 { }
public class BaseGeneric : IBaseGeneric { }
public class BaseGeneric2 : IBaseGeneric, IInterfaceBidon { }
public interface IBaseGeneric { }
public class ChildGeneric : BaseGeneric { }
public interface IChildGeneric : IBaseGeneric { }
public class ChildGeneric2 : BaseGeneric { }
public interface IChildGeneric2 : IBaseGeneric { }

public class WrongBaseGeneric { }
public interface IWrongBaseGeneric { }

public interface IInterfaceBidon { }

public class ClassA { }
public class ClassB { }
public class ClassC { }
public class ClassB2 : ClassB { }
public class BaseGenericA : IBaseGenericA { }
public class BaseGenericB { }
public interface IBaseGenericB { }
public class BaseGenericA2 : IBaseGenericA, IInterfaceBidonA { }
public interface IBaseGenericA { }
public class ChildGenericA : BaseGenericA { }
public interface IChildGenericA : IBaseGenericA { }
public class ChildGenericA2 : BaseGenericA { }
public class ChildGenericA3 : BaseGenericB { }
public class ChildGenericA4 : IBaseGenericB { }
public interface IChildGenericA2 : IBaseGenericA { }

public class WrongBaseGenericA { }
public interface IWrongBaseGenericA { }

public interface IInterfaceBidonA { }