如何在运行时可靠检测动态加载的DLL是否已卸载？

我在.NET 7 WPF应用中有这样的场景：数据网格列使用用户自定义的C#脚本，用户修改脚本后会编译生成新的DLL，这时候需要卸载旧版本的DLL。

按照官方文档的思路做了测试，用自定义AssemblyLoadContext加载DLL，但遇到了异常情况：

• 点击Button1调用RunTest方法时，从创建上下文、加载DLL、执行逻辑到卸载的流程是完整的，之后弱引用的IsAlive会变为false，符合预期
• 但把逻辑拆分成RunTest2和Button2_Click两个阶段后，先创建上下文再执行卸载，弱引用的IsAlive始终为true，不过VS的「Modules」窗口里已经看不到这个DLL了

我想搞清楚：是我对弱引用的使用有误，还是对VS模块窗口的理解有偏差？另外，有没有一种可靠的方法可以检测DLL是否已经被卸载？

测试代码如下：

private void Button1_Click(object sender, RoutedEventArgs e)
{
    var spo = model.GetDataObject(0);
    RunTest(spo, @"dll_2098706330365.dll");  // 正常工作
    RunTest2(spo, @"dll_2098706330365.dll"); // 异常
}
private void Button2_Click(object sender, RoutedEventArgs e)
{
    WeakReference weakRef;
    TestUnload22(alc, out weakRef);
    TestUnload23(weakRef);
}
MyAssemblyLoader alc;
public void RunTest(DataObject spo, string path)
{
    WeakReference weakRef;
    TestUnload(path, spo, out weakRef);

    for (int i = 0; weakRef.IsAlive && (i < 10); i++)
    {
        GC.Collect();
        GC.WaitForPendingFinalizers();

        Debug.WriteLine("    >>> UnloadTest: attemtp: {0} Weak ref {1}", i, weakRef.IsAlive);
    }

    Debug.WriteLine(">>> RunTest: ended {0}", weakRef.IsAlive);
}
[MethodImpl(MethodImplOptions.NoInlining)]
private void TestUnload(string path, DataObject spo, out WeakReference weakRef)
{
    var alc = new MyAssemblyLoader (path);
    Assembly a = alc.LoadFromAssemblyPath(path);

    weakRef = new WeakReference(alc, trackResurrection: true);

    var scriptInstance = InstantiateScript(a);

    var result = scriptInstance.Evaluate(spo, null)?.ToString();

    Debug.WriteLine("    >>>  Evaluate: " + result);

    alc.Unload();
}
public void RunTest2(ISPDataObject spo, string path)
{
    TestUnload2(path, spo);
}
[MethodImpl(MethodImplOptions.NoInlining)]
private void TestUnload2(string path, ISPDataObject spo)
{
    alc = new MyAssemblyLoader (path);
    Assembly a = alc.LoadFromAssemblyPath(path);
}
[MethodImpl(MethodImplOptions.NoInlining)]
private void TestUnload22(MyAssemblyLoader alc, out WeakReference weakRef)
{
    weakRef = new WeakReference(alc, trackResurrection: true);
    alc.Unload();
}
private void TestUnload23(WeakReference weakRef)
{
    for (int i = 0; weakRef.IsAlive && (i < 10); i++)
    {
        GC.Collect();
        GC.WaitForPendingFinalizers();

        Debug.WriteLine("    >>> UnloadTest2: attemtp: {0} Weak ref {1}", i, weakRef.IsAlive);
    }

    Debug.WriteLine(">>> RunTest2: ended {0}", weakRef.IsAlive);
}

内容的提问来源于stack exchange，提问作者Boppity Bop