how to find every class that derives from class code example

Example 1: c# get all inherited classes of a class

//through reflection
using System.Reflection;

//as a reusable method/function
Type[] GetInheritedClasses(Type MyType) 
{
  	//if you want the abstract classes drop the !TheType.IsAbstract but it is probably to instance so its a good idea to keep it.
	return Assembly.GetAssembly(MyType).GetTypes().Where(TheType => TheType.IsClass && !TheType.IsAbstract && TheType.IsSubclassOf(MyType));
}

//or as a selection of a type in code.
Type[] ChildClasses Assembly.GetAssembly(typeof(YourType)).GetTypes().Where(myType => myType.IsClass && !myType.IsAbstract && myType.IsSubclassOf(typeof(YourType))));

//Example of usage
foreach (Type Type in
                Assembly.GetAssembly(typeof(BaseView)).GetTypes()
                .Where(TheType => TheType.IsClass && !TheType.IsAbstract && TheType.IsSubclassOf(typeof(BaseView))))
            {

                AddView(Type.Name.Replace("View", ""), (BaseView)Activator.CreateInstance(Type));
            }

Example 2: get all classes that extend a class c#

public static class ReflectiveEnumerator
{
    static ReflectiveEnumerator() { }

    public static IEnumerable<T> GetEnumerableOfType<T>(params object[] constructorArgs) where T : class, IComparable<T>
    {
        List<T> objects = new List<T>();
        foreach (Type type in 
            Assembly.GetAssembly(typeof(T)).GetTypes()
            .Where(myType => myType.IsClass && !myType.IsAbstract && myType.IsSubclassOf(typeof(T))))
        {
            objects.Add((T)Activator.CreateInstance(type, constructorArgs));
        }
        objects.Sort();
        return objects;
    }
}