winform对于菜单项禁用的理解

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Linq;
  4 using System.Text;
  5 using System.Drawing;
  6 using System.Windows.Forms;
  7 
  8 namespace StandardMenu
  9 {
 10     class StandardMenu:Form
 11     {
 12         MenuItem miFileOpen, miFileSave;
 13         MenuItem miEditCut, miEditCopy, miEditPaste;
 14 
 15         //for popup code
 16         bool bDocumentPresent = true;
 17         bool bNonNullSelection = false;
 18         bool bStuffInClipboard = true;
 19 
 20         static void Main(string[] args)
 21         {
 22             Application.Run(new StandardMenu());
 23         }
 24         public StandardMenu()
 25         {
 26             Text = "Standard Menu!";
 27             Menu = new MainMenu();
 28 
 29             //File
 30             MenuItem mi = new MenuItem("&File");
 31             mi.Popup += new EventHandler(MenuFileOnPopup);
 32             Menu.MenuItems.Add(mi);
 33             int index = Menu.MenuItems.Count - 1;
 34 
 35             //测试index
 36             //在File处，index值是1
 37             Console.WriteLine(Menu.MenuItems.Count);
 38 
 39             //Fiel Open
 40             miFileOpen = new MenuItem("&Open...");
 41             miFileOpen.Click += new EventHandler(miFileOpen_Click);
 42             miFileOpen.Shortcut = Shortcut.CtrlO;
 43             Menu.MenuItems[index].MenuItems.Add(miFileOpen);
 44 
 45             //File Save
 46             miFileSave = new MenuItem("&Save");
 47             miFileSave.Click += new EventHandler(miFileSave_Click);
 48             miFileSave.Shortcut = Shortcut.CtrlS;
 49             Menu.MenuItems[index].MenuItems.Add(miFileSave);
 50 
 51             //Horizontal Line
 52             mi = new MenuItem("-");
 53             Menu.MenuItems[index].MenuItems.Add(mi);
 54 
 55             //File Exit
 56             mi = new MenuItem("&E&xit");
 57             mi.Click += new EventHandler(miFileEdit_Click);
 58             Menu.MenuItems[index].MenuItems.Add(mi);
 59 
 60             //Edit
 61             mi = new MenuItem("&Edit");
 62             mi.Popup +=new EventHandler(MenuEditOnPopup);
 63             Menu.MenuItems.Add(mi);
 64             index = Menu.MenuItems.Count - 1;
 65 
 66             //测试index
 67             //在Edit处，index值是2
 68             Console.WriteLine(Menu.MenuItems.Count);
 69 
 70             //Edit Cut
 71             miEditCut = new MenuItem("Cu&t");
 72             miEditCut.Click += new EventHandler(miEditCut_Click);
 73             miEditCut.Shortcut = Shortcut.CtrlX;
 74             Menu.MenuItems[index].MenuItems.Add(miEditCut);
 75 
 76             //Edit Copy
 77             miEditCopy = new MenuItem("&Copy");
 78             miEditCopy.Click += new EventHandler(miEditCopy_Click);
 79             miEditCopy.Shortcut = Shortcut.CtrlC;
 80             Menu.MenuItems[index].MenuItems.Add(miEditCopy);
 81 
 82             //Edit Paste
 83             miEditPaste = new MenuItem("&Paste");
 84             miEditPaste.Click += new EventHandler(miEditPaste_Click);
 85             miEditPaste.Shortcut = Shortcut.CtrlV;
 86             Menu.MenuItems[index].MenuItems.Add(miEditPaste);
 87 
 88             // Help
 89             mi = new MenuItem("&Help");
 90             Menu.MenuItems.Add(mi);
 91             index = Menu.MenuItems.Count - 1;
 92 
 93             //测试index
 94             //在Help处，index值是3
 95             Console.WriteLine(Menu.MenuItems.Count);
 96 
 97             // Help About
 98             mi = new MenuItem("&About StandarMenu...");
 99             mi.Click +=new EventHandler(MenuHelpAboutOnClick);
100             Menu.MenuItems[index].MenuItems.Add(mi);
101         }
102 
103         void MenuEditOnPopup(object sender, EventArgs e)
104         {
105             miEditCut.Enabled = bNonNullSelection;
106             miEditCopy.Enabled = bNonNullSelection;
107             miEditPaste.Enabled = bStuffInClipboard;
108         }
109 
110         void MenuHelpAboutOnClick(object sender, EventArgs e)
111         {
112             MessageBox.Show("This should be a File About box!", Text);
113         }
114 
115         void miEditPaste_Click(object sender, EventArgs e)
116         {
117             MessageBox.Show("This should be a File Edit Paste dialog box!", Text);
118         }
119 
120         void miEditCopy_Click(object sender, EventArgs e)
121         {
122             MessageBox.Show("This should be a File Edit Save dialog box!", Text);
123         }
124 
125         void miEditCut_Click(object sender, EventArgs e)
126         {
127             MessageBox.Show("This should be a File Edit Cut dialog box!", Text);
128         }
129 
130         void miFileEdit_Click(object sender, EventArgs e)
131         {
132             Close();
133         }
134 
135         void miFileSave_Click(object sender, EventArgs e)
136         {
137             MessageBox.Show("This should be a File Save dialog box!", Text);
138         }
139 
140         void miFileOpen_Click(object sender, EventArgs e)
141         {
142             MessageBox.Show("This should be a File Open dialog box!",Text);
143         }
144 
145         void MenuFileOnPopup(object sender, EventArgs e)
146         {
147             miFileSave.Enabled = bDocumentPresent;
148         }
149     }
150 }

以上代码中禁用了“复制”和“剪切”菜单，所以从下图可以看出禁用的实际效果 。

还有，代码中的Menu.MenuItems.Count是随着主菜单项的加入，逐渐增加的；