Check if a class is derived from a generic class

Asked 2009-01-19T14:10:18.140

364

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

public class GenericClass<T> : GenericInterface<T>
{
}

public class Test : GenericClass<SomeType>
{
}

Is there any way to find out if a Type object is derived from GenericClass?

t.IsSubclassOf(typeof(GenericClass<>))

does not work.

c# generics reflection

Edit Report

2 Answers

I worked through some of these samples and found they were lacking in some cases. This version works with all kinds of generics: types, interfaces and type definitions thereof.

public static bool InheritsOrImplements(this Type child, Type parent)
{
    parent = ResolveGenericTypeDefinition(parent);

    var currentChild = child.IsGenericType
                           ? child.GetGenericTypeDefinition()
                           : child;

    while (currentChild != typeof (object))
    {
        if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
            return true;

        currentChild = currentChild.BaseType != null
                       && currentChild.BaseType.IsGenericType
                           ? currentChild.BaseType.GetGenericTypeDefinition()
                           : currentChild.BaseType;

        if (currentChild == null)
            return false;
    }
    return false;
}

private static bool HasAnyInterfaces(Type parent, Type child)
{
    return child.GetInterfaces()
        .Any(childInterface =>
        {
            var currentInterface = childInterface.IsGenericType
                ? childInterface.GetGenericTypeDefinition()
                : childInterface;

            return currentInterface == parent;
        });
}

private static Type ResolveGenericTypeDefinition(Type parent)
{
    var shouldUseGenericType = true;
    if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
        shouldUseGenericType = false;

    if (parent.IsGenericType && shouldUseGenericType)
        parent = parent.GetGenericTypeDefinition();
    return parent;
}

Here are the unit tests also:

protected interface IFooInterface
{
}

protected interface IGenericFooInterface<T>
{
}

protected class FooBase
{
}

protected class FooImplementor
    : FooBase, IFooInterface
{
}

protected class GenericFooBase
    : FooImplementor, IGenericFooInter


                        
                        
                            answered 2011-02-04T11:21:20.177


            
            
                
                    
                        
                            
                            
                        
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                        JaredPar's code works but only for one level of inheritance.  For unlimited levels of inheritance, use the following code

public bool IsTypeDerivedFromGenericType(Type typeToCheck, Type genericType)
{
    if (typeToCheck == typeof(object))
    {
        return false;
    }
    else if (typeToCheck == null)
    {
        return false;
    }
    else if (typeToCheck.IsGenericType && typeToCheck.GetGenericTypeDefinition() == genericType)
    {
        return true;
    }
    else
    {
        return IsTypeDerivedFromGenericType(typeToCheck.BaseType, genericType);
    }
}


                        
                        
                            answered 2009-01-19T17:21:47.020



        
        
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