try

this.close();

或

this.dispose();

try

this.close();

or

this.dispose();

几天前，有人问了类似的问题.

此处:如何在子表单中关闭父表单 [ ^ ]

您可以隐藏ParentForm，因为您无法将其关闭. ParentForm是父表单，除非子表单已关闭，否则无法关闭.

Similar question was asked couple of days back.

Here: How to close parent form in child form[^]

You can just hide ParentForm as you cannot close it. ParentForm is parent form and it cannot be closed unless child form is closed.