怎么能反思.发出、赋值不兼容的类型

我有两个简单的类。

public class A { }
public class B { }

我像下面这样构建和实例化类C。

var assemblyBuilder = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName("Some.Namespace"), AssemblyBuilderAccess.Run);
var moduleBuilder = assemblyBuilder.DefineDynamicModule(assemblyBuilder.GetName().Name);
// public class C
var typeBuilder = moduleBuilder.DefineType("C", TypeAttributes.Public | TypeAttributes.Class, typeof(object));
// public A A;
var aField = typeBuilder.DefineField("A", typeof(A), FieldAttributes.Public);
// public C() { this.A = new B(); } !!!!
var ctorBuilder = typeBuilder.DefineConstructor(MethodAttributes.Public, CallingConventions.HasThis, Type.EmptyTypes);
var ctorIL = ctorBuilder.GetILGenerator();
ctorIL.Emit(OpCodes.Ldarg_0);
ctorIL.Emit(OpCodes.Newobj, typeof(B).GetConstructor(Type.EmptyTypes));
ctorIL.Emit(OpCodes.Stfld, aField);
ctorIL.Emit(OpCodes.Ret);
// return new C();
var type = typeBuilder.CreateType();
return Activator.CreateInstance(type);

问题是我可以成功实例化类C。当我检查C.A的类型和值时，我感到非常惊讶。

var c = CreateC();
var field = c.GetType().GetField("A");
var fieldValue = c.GetType().GetField("A").GetValue(c);
Console.WriteLine(typeof(A) == field.FieldType);      // True
Console.WriteLine(typeof(A) == fieldValue.GetType()); // False
Console.WriteLine(typeof(B) == field.FieldType);      // False   
Console.WriteLine(typeof(B) == fieldValue.GetType()); // True

简单地说，我有以下类正在工作!

public class A { }
public class B { }
public class C 
{
    public A A;
    public C() 
    {
        this.A = new B();
    }
}

我的问题是:

1. 这怎么可能?
2. CLR在哪个级别检查类型?