Prevent duplicate MDI children forms
问题 Is there a way to prevent the opening of a certain form within an MDI container if that said form is already opened? 回答1: You can interate over the OpenForms collection to check if there is already a form of the given type: foreach (Form form in Application.OpenForms) { if (form.GetType() == typeof(MyFormType)) { form.Activate(); return; } } Form newForm = new MyFormType(); newForm.MdiParent = this; newForm.Show(); 回答2: AFAIK there is no standard way. You'll have to implement it yourself. I'd