首先在MDI的主窗體中：

1．在主窗體建構函式中，新增如下程式碼，注意要在InitializeComponent呼叫之後，如：

//Add File Menu

MenuItem miFile = mnuMain.MenuItems.Add("&File");

miFile.MergeOrder=1;

miFile.MergeType = MenuMerge.MergeItems;

MenuItem miAddDoc = new MenuItem( "&Add Document",

new EventHandler(this.FileAdd_Clicked),

Shortcut.CtrlA );

miAddDoc.MergeOrder=100;

MenuItem miExit = new MenuItem( "E&xit",

new EventHandler(this.FileExit_Clicked),

Shortcut.CtrlX );

miExit.MergeOrder=110;

miFile.MenuItems.Add(miAddDoc);

miFile.MenuItems.Add("-");// Give a seperator

miFile.MenuItems.Add(miExit);

//Add Window Menu

MenuItem miWindow = mnuMain.MenuItems.Add("&Window");

miWindow.MergeOrder = 10;

miWindow.MenuItems.Add( "&Cascade",

new EventHandler(this.WindowCascade_Clicked));

miWindow.MenuItems.Add( "Tile &Horizontal",

new EventHandler(this.WindowTileH_Clicked));

miWindow.MenuItems.Add( "Tile &Vertical",

new EventHandler(this.WindowTileV_Clicked));

miWindow.MdiList = true

2．然後為相應的Menu_Click事件定義函式，如：

#region MENU_CLICK_MESSAGE_HANDLE

//File->Add Menu item handler

protected void FileAdd_Clicked(object sender, System.EventArgs e)

{

AddMDIChild() ; //Create new MDI child window

}

//File->Exit Menu item handler

protected void FileExit_Clicked(object sender, System.EventArgs e)

{

this.Close();

}

//Window->Cascade Menu item handler

protected void WindowCascade_Clicked(object sender, System.EventArgs e)

{

this.LayoutMdi(MdiLayout.Cascade);

}

//Window->Tile Horizontally Menu item handler

protected void WindowTileH_Clicked(object sender, System.EventArgs e)

{

this.LayoutMdi(MdiLayout.TileHorizontal);

}

//Window->Tile Vertically Menu item handler

protected void WindowTileV_Clicked(object sender, System.EventArgs e)

{

this.LayoutMdi(MdiLayout.TileVertical);

}

#endregion {MENU_CLICK_MESSAGE_HANDLE}

3．建立子窗體，如：

//Add a new child window if it doesn’t exist; else set focus on it

private void AddMDIChild()

{

// MyChildForm is the one I'm looking for

MDIChild myMDIChild = null;

foreach(Form f in this.MdiChildren)

{

if(f is MDIChild)

{

// found it

myMDIChild = (MDIChild) f;

break;

}

}

if( myMDIChild != null)

{

myMDIChild.Show();

myMDIChild.Focus();

}

else

{

myMDIChild = new MDIChild();

myMDIChild.MdiParent = this;

myMDIChild.Show();

myMDIChild.Focus();

}

}

當完成上面的步驟後，主窗體執行的效果如下圖所示：

然後在子窗體中，具體操作如下：

1．在子窗體建構函式中，新增如下程式碼，同樣要在InitializeComponent呼叫之後，如：

//Add File Menu

MenuItem miFile = mnuChildMain.MenuItems.Add("&File");

miFile.MergeType = MenuMerge.MergeItems;

miFile.MergeOrder = 1;

MenuItem miLoadDoc = miFile.MenuItems.Add( "&Load Document",

new EventHandler(this.LoadDocument_Clicked) );

miLoadDoc.MergeOrder = 105;

//Add Formatting Menu

MenuItem miFormat = mnuChildMain.MenuItems.Add("F&ormat");

miFormat.MergeType = MenuMerge.Add;

miFormat.MergeOrder = 5;

//Font Face sub-menu

miSansSerif = new MenuItem("&1." + sansSerifFontFamily.Name,

new EventHandler(this.FormatFont_Clicked));

miSerif = new MenuItem("&2." + serifFontFamily.Name,

new EventHandler(this.FormatFont_Clicked));

miMonoSpace = new MenuItem("&3." + monoSpaceFontFamily.Name,

new EventHandler(this.FormatFont_Clicked));

miSansSerif.Checked = true ;

miFormatFontChecked = miSansSerif ;

miSansSerif.DefaultItem = true ;

miFormat.MenuItems.Add( "Font &Face"

, (new MenuItem[]{ miSansSerif, miSerif, miMonoSpace })

);

//Font Size sub-menu

miSmall = new MenuItem("&Small", new EventHandler(this.FormatSize_Clicked));

miMedium = new MenuItem("&Medium", new EventHandler(this.FormatSize_Clicked));

miLarge = new MenuItem("&Large", new EventHandler(this.FormatSize_Clicked));

miMedium.Checked = true ;

miMedium.DefaultItem = true ;

miFormatSizeChecked = miMedium ;

miFormat.MenuItems.Add( "Font &Size"

, (new MenuItem[]{ miSmall, miMedium, miLarge })

);

2．然後為相應的Menu_Click事件定義函式，如：

#region MENU_CLICK_MESSAGE_HANDLE

//File->Load Document Menu item handler

protected void LoadDocument_Clicked(object sender, System.EventArgs e)

{

MessageBox.Show(this.Text) ;

}

//Format->Font Menu item handler

protected void FormatFont_Clicked(object sender, System.EventArgs e)

{

MenuItem miClicked = (MenuItem)sender;

miClicked.Checked = true;

miFormatFontChecked.Checked = false;

miFormatFontChecked = miClicked ;

if (miClicked == miSansSerif)

{

currentFontFamily = sansSerifFontFamily ;

}

else if (miClicked == miSerif)

{

currentFontFamily = serifFontFamily ;

}

else

{

currentFontFamily = monoSpaceFontFamily ;

}

rtbDoc.Font = new Font(currentFontFamily, fontSize);

}

//Format->Size Menu item handler

protected void FormatSize_Clicked(object sender, System.EventArgs e)

{

MenuItem miClicked = (MenuItem)sender;

miClicked.Checked = true;

miFormatSizeChecked.Checked = false;

miFormatSizeChecked = miClicked;

if (miClicked == miSmall)

{

fontSize = FontSizes.Small ;

}

else if (miClicked == miLarge)

{

fontSize = FontSizes.Large ;

}

else

{

fontSize = FontSizes.Medium ;

}

rtbDoc.Font = new Font(currentFontFamily, fontSize);

}

#endregion {MENU_CLICK_MESSAGE_HANDLE}

3．窗體的私有成員：

private struct FontSizes

{

public static float Small = 8f;

public static float Medium = 12f;

public static float Large = 24f;

}

private float fontSize = FontSizes.Medium;

private MenuItem miFormatFontChecked;

private MenuItem miFormatSizeChecked;

private MenuItem miSmall ;

private MenuItem miMedium ;

private MenuItem miLarge ;

private MenuItem miSansSerif ;

private MenuItem miSerif ;

private MenuItem miMonoSpace ;

private FontFamily currentFontFamily ;

private FontFamily monoSpaceFontFamily;

private FontFamily sansSerifFontFamily;

private System.Windows.Forms.MainMenu mnuChildMain;

private FontFamily serifFontFamily;

這樣，子窗體的程式碼也完成了，展現的效果如下圖所示：

其實在做MDI子窗體上的選單要和主窗體上的選單合併，主要是設定每個選單的MergeOrder，對於每個選單的MergeOrder設定不同的值，從而達到合併後的效果。以下用表格說明：

注：紅色表示每個選單的MergeOrder值

合併後的效果如下：

注：紅色表示每個選單的MergeOrder值

所以如果想在MDI子窗體上的選單和主窗體上的選單合併後，達到所預期的效果，就必須好好涉及它們之間的MergeOrder，大致如下：

1．如果和主窗體原有的選單列進行合併，首先把根選單的MergeOrder設定與主窗體相應選單一樣的MergeOrder值，同時設定MenuItem的MergeType為MenuMerge.MergeItems，合併後在此列選單中的位置，就看每個選單的MergeOrder了。

2．如果想在主窗體新增新的選單列，MenuItem的MergeType為MenuMerge. Add，選單列插入的位置，要看其MergeOrder了。