c# – 为什么基础Windows窗体的类与泛型类型停止设计器加载？

public partial class Base<T> : Form where T : BaseClass
{
    private GenericHandler handler = new GenericHandler();
}

public class BaseClass { }

public class GenericHandler
{
    public void DoSomethingWithInstance<T>(T instance) where T : BaseClass
    {

    }
}

我的设计师类声明也反映了我的形式.现在当我做了代表Foo类型的第二个表单时,我无法访问设计器,因为我收到这个错误：

The designer could not be shown for this file because none of the
classes within it can be designed. The designer inspected the
following classes in the file: Foo — The base class
‘WindowsFormsApplication1.Base’ could not be loaded. Ensure the
assembly has been referenced and that all projects have been built.

FooClass — The base class ‘WindowsFormsApplication1.BaseClass’
cannot be designed.

public partial class Foo : Base<FooClass>
{
    public Foo()
    {
        InitializeComponent();
    }
}

public class FooClass : BaseClass { }

为什么会发生这种情况/我做错了什么或有什么其他方法可以做到这一点？