Csharp try 访问字典中的模拟对象时引发KeyNotFoundException

我的模拟测试是KeyNotFoundException分:

[Fact]
public void MockAssembly_GetTypes_ReturnsMockedTypes()
{
    var mockAssembly = new Mock<Assembly>();

    mockAssembly.Setup(a => a.GetTypes()).Returns(new Type[] { typeof(MyClass) });
    var mockAssemblyObject = mockAssembly.Object;

    var assemblyDictionary = new Dictionary<Assembly, HashSet<Type>>();
    if (!assemblyDictionary.TryGetValue(mockAssemblyObject, out var types))
    {
        types = new HashSet<Type>(mockAssemblyObject.GetTypes());
        assemblyDictionary[mockAssemblyObject] = types;
    }

    Assert.Contains(mockAssemblyObject, assemblyDictionary.Keys);
    Assert.Single(assemblyDictionary[mockAssemblyObject]);
}

System.Collections.Generic.KeyNotFoundException:字典中不存在给定的键"".

在Assert.Single(assemblyDictionary[mockAssemblyObject]);号线上

即使嘲笑GetHashCode也无济于事--它仍然试图使用空键.

为什么会发生这种事？

编辑:

进一步的测试表明，如果我调用assemblyDictionary.TryGetValue(mockAssemblyObject, out var myTypes);，即使在我使用assemblyDictionary.Add(mockAssemblyObject, types)添加之后，结果也是假的和空的.