那是因为 CheckBox 助手生成了一个与复选框同名的附加隐藏字段(您可以通过浏览生成的源代码):

That's because the CheckBox helper generates an additional hidden field with the same name as the checkbox (you can see it by browsing the generated source code):

<input checked="checked" id="Visible" name="Visible" type="checkbox" value="true" />
<input name="Visible" type="hidden" value="false" />

因此，当您提交表单时，两个值都会发送到控制器操作.以下是直接来自 ASP.NET MVC 源代码的注释，解释了此附加隐藏字段背后的原因:

So both values are sent to the controller action when you submit the form. Here's a comment directly from the ASP.NET MVC source code explaining the reasoning behind this additional hidden field:

if (inputType == InputType.CheckBox) {
    // Render an additional <input type="hidden".../> for checkboxes. This
    // addresses scenarios where unchecked checkboxes are not sent in the request.
    // Sending a hidden input makes it possible to know that the checkbox was present
    // on the page when the request was submitted.
    ...

我建议您使用视图模型作为动作参数或直接使用标量类型，而不是使用 FormCollection，并将解析的麻烦留给默认模型绑定器:

Instead of using FormCollection I would recommend you using view models as action parameters or directly scalar types and leave the hassle of parsing to the default model binder:

public ActionResult SomeAction(bool visible)
{
    ...
}