您可以检查表单是否已经打开：

Form instance = null; // Looking for MyForm among all opened forms foreach (Form form in Application.OpenForms) if (form is MyForm) { instance = form; break; } if (Object.ReferenceEquals(null, instance)) { // No opened form, lets create it and show up: instance = new MyForm(); instance.Show(); ... } else { // MyForm has been already opened // Lets bring it to front, focus, restore it sizes (if minimized) if (instance.WindowState == FormWindowState.Minimized) instance.WindowState = FormWindowState.Normal; instance.BringToFront(); if (instance.CanFocus) instance.Focus(); ... } 

也许这可以帮助你：

 public static bool formOpened = false; // it is global boolean Form2 instance; 

当您打开表单时：

 if(formOpened == false) { instance = new Form2(); instance.Show(); formOpened = true; } else { instance.Focus(); } 

还有一件事是在关闭Form2之后，你应该将formOpened的值设置为false;

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