查找泛型类的所有派生类型

Question

我有一个泛型类和一个派生类，如下所示。

public class GenericClass<T> { ... }

public class DerivedClass : GenericClass<SomeType> { ... }

如何通过反射找到派生类？我已经尝试过以下两种方法，但似乎不起作用。

System.Reflection.Assembly.GetExecutingAssembly().GetTypes().Where(t => typeof(GenericClass<>).IsAssignableFrom(t));

System.Reflection.Assembly.GetExecutingAssembly().GetTypes().Where(t => t.IsSubclassOf(typeof(GenericClass<>));

Answer 1

var result = System.Reflection.Assembly.GetExecutingAssembly()
    .GetTypes()
    .Where(t => t.BaseType != null && t.BaseType.IsGenericType && 
                t.BaseType.GetGenericTypeDefinition() == typeof(GenericClass<>));

Answer 2

比这更复杂一点。 t.BaseType 可能返回 null（例如，当 t 是接口时）。另请注意，Type.IsSubclassOf方法不适用于泛型类型！如果您正在处理泛型类型，则应该使用 GetTypeDefinition 方法。我最近在博客中介绍了如何获取类的所有派生类型。这是一个也适用于泛型的 IsSubclass 方法：

public static bool IsSubclassOf(Type type, Type baseType)
{
    if (type == null || baseType == null || type == baseType)
        return false;

    if (baseType.IsGenericType == false)
    {
        if (type.IsGenericType == false)
            return type.IsSubclassOf(baseType);
    }
    else
    {
        baseType = baseType.GetGenericTypeDefinition();
    }

    type = type.BaseType;
    Type objectType = typeof(object);
    while (type != objectType && type != null)
    {
        Type currentType = type.IsGenericType
            ? type.GetGenericTypeDefinition()
            : type;
        if (currentType == baseType)
            return true;

        type = type.BaseType;
     }

    return false;
}

Answer 3

因为我需要递归地查找所有派生类型，所以我编写了此代码并将与可能需要它的任何人共享：

    public void ListAllDerviedTypes()
    {
        Type entityType = typeof(TableAdapter);
        Assembly assembly = Assembly.LoadFrom(entityType.Assembly.Location);
        Type[] types = assembly.GetTypes();

        List<Type> results = new List<Type>();
        GetAllDerivedTypesRecursively(types, typeof(SiteAndSectorsTable<>), ref results);

        foreach (var type in results)
        {
            Console.WriteLine(type.Name);
        }
    }

    private static void GetAllDerivedTypesRecursively(Type[] types, Type type1, ref List<Type> results)
    {
        if (type1.IsGenericType)
        {
            GetDerivedFromGeneric(types, type1, ref results);
        }
        else
        {
            GetDerivedFromNonGeneric(types, type1, ref results);
        }
    }

    private static void GetDerivedFromGeneric(Type[] types, Type type, ref List<Type> results)
    {
        var derivedTypes = types
            .Where(t => t.BaseType != null && t.BaseType.IsGenericType &&
                        t.BaseType.GetGenericTypeDefinition() == type).ToList();
        results.AddRange(derivedTypes);
        foreach (Type derivedType in derivedTypes)
        {
            GetAllDerivedTypesRecursively(types, derivedType, ref results);
        }
    }


    public static void GetDerivedFromNonGeneric(Type[] types, Type type, ref List<Type> results)
    {
        var derivedTypes = types.Where(t => t != type && type.IsAssignableFrom(t)).ToList();

        results.AddRange(derivedTypes);
        foreach (Type derivedType in derivedTypes)
        {
            GetAllDerivedTypesRecursively(types, derivedType, ref results);
        }
    } 

Answer 4

Kim 的答案的改进（较短）版本：

    public List<Type> GetAllDerivedTypes(Type baseType)
    {
        Assembly assembly = Assembly.LoadFrom(baseType.Assembly.Location);
        Type[] typesInAssembly = assembly.GetTypes();

        var results = new List<Type>();
        GetAllDerivedTypesRecursively(typesInAssembly, baseType, ref results);

        return results;
    }

    private static void GetAllDerivedTypesRecursively(Type[] types, Type baseType, ref List<Type> results)
    {
        Type[] derivedTypes;

        if (baseType.IsGenericType)
            derivedTypes = types.Where(t => t.BaseType != null && t.BaseType.IsGenericType && t.BaseType.GetGenericTypeDefinition() == baseType).ToArray();
        else
            derivedTypes = types.Where(t => t != baseType && baseType.IsAssignableFrom(t)).ToArray();

        results.AddRange(derivedTypes);

        foreach (Type derivedType in derivedTypes)
            GetAllDerivedTypesRecursively(types, derivedType, ref results);
    }