使用表单(Working with Forms)

 我正在编写一个程序，使用2种形式，主要形式和配置形式，因此当用户单击工具栏菜单 - >首选项时，将显示首选项表单，并且我希望它使用户只能够拥有一次一个首选项。 
 
 当我使用： 
 
    Prefs preferencias = new Prefs;

    private void preferenciasToolStripMenuItem_Click(object sender, EventArgs e)   
    {
        preferencias.Show();
    }
 
 它可以工作，但是当我关闭“首选项”窗体并尝试打开一个新窗体时，程序崩溃。 
 
 而当我使用： 
 
    private void preferenciasToolStripMenuItem_Click(object sender, EventArgs e)   
    {
        Prefs preferencias = new Prefs;
        preferencias.Show();
    }
 
 用户可以拥有多个首选项表单。 
 
 我能做什么？ 
 
 提前致谢。 

I'im writing a program that works with 2 forms, the main form and the form where the configuration is made, so when the user clicks toolstripmenu->Preferences the Preferences form is showned and I want it to make the user only capable of having one Preferences form at a time.
 
When I use:
 
    Prefs preferencias = new Prefs;

    private void preferenciasToolStripMenuItem_Click(object sender, EventArgs e)   
    {
        preferencias.Show();
    }
 
It works, but when I close the Preferences form and try to open a new one the program crashes.
 
And When I use:
 
    private void preferenciasToolStripMenuItem_Click(object sender, EventArgs e)   
    {
        Prefs preferencias = new Prefs;
        preferencias.Show();
    }
 
The user can hav multiple Preferences form.
 
What can I do?
 
Thanks in advance.

原文：https://stackoverflow.com/questions/1256415