以MDI形式多次預防相同的子窗口

Question

我正在研究c＃桌面應用程序，在MDI窗體中，當您單擊菜單時打開相同的子窗口，同時存在該窗口的第一個實例。 如何防止MDI窗體中的這些多個子窗口實例？

Answer 1

如果表單已被打開，您可以查看：

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(); 
    ... 
    } 

Answer 2

也許這可以幫助你：

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

當你打開你的表單：

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

還有一事情是在你的Form2被關閉之後，你應該將formOpened的值設置爲false;