问答题
[说明]
以下代码实现了当用户推出界面时，判断TextEdit中的文字是否发生改变，弹出对话框判断，让用户选择选择是否保存文件或取消退出界面操作。阅读下面代码，补充完整。
[代码7-1]
Begin VB.Form Forml
//...窗体描述(略)
Begin VB.TextBox TextEdit
Height = 1830
Left = 180
TabIndex = 0
Text = "TextEdit"
Top = 360
Width = 3885
End
//...窗体描述(略)
End
[代码 7-2]
Dim txtchange As Boolean
Dim myval As String
Private Sub Form Load ( )
TextEdit.Text = "CIU, 中国软考联盟!
txtchange = False
End Sub
[代码 7-3]
Private Sub TextEdit_Change ( )
Static notchange As Boolean
{{U}} (1) {{/U}}
{{U}} (2) {{/U}}
End Sub
Private Sub Form_Unload ( Cancel As Integer )
Dim myval As String
If {{U}}(3) {{/U}} Then
myval = MsgBox ( "保存文件的更改吗?", vbYesNoCancel, "提示信息" )
If {{U}}(4) {{/U}} Then
MsgBox "保存成功"
End
End If
If {{U}}(5) {{/U}} Then End
If {{U}}(6) {{/U}} Then Cancel = 1
End If
End Sub