Developing Pocket PC Applications In Visual Studio.NET  : Page 3

Figure 8. Setting the form's MinimizeBox property to False causes the OK button to appear.

Setting Form Properties and Coding Event Handlers
Setting the MinimizeBox property of the Windows Form to False causes it to display the OK button ; otherwise, it displays an "X". Clicking on the OK button closes the application, whereas the clicking the "X" minimizes the application window. When you are debugging your application, clicking on the OK button terminates the debugging process in Visual Studio .NET; but if you click the "X" button, you have to terminate the debugging process in Visual Studio .NET manually.

To summarize, the OK button terminates the application, whereas the "X" button minimizes the application. Figure 8 shows how the setting affects the final form's title bar.

Activate the Menus
Now, you can activate the menus. But first, you must write the code for the File menu. The first menu item is the New item:

   Private Sub mnuNew_Click(ByVal sender As _
      System.Object, ByVal e As System.EventArgs) _
      Handles mnuNew.Click
      Dim response As Microsoft.VisualBasic.MsgBoxResult
      response = MsgBox("Save existing file?", _
         MsgBoxStyle.OKCancel, "Save")
      If response = MsgBoxResult.OK Then
         Save()
      Else
         Return
      End If
      TextBox1.Text = ""
      currentFilename = ""
      StatusBar1.Text = "New"
   End Sub

When users click on the New item, the application first displays a message box asking if they want to save the file. If so, the code calls the Save() method and resets the form; otherwise, it exits.

Next, the Open item prompts users to enter a filename using the OpenFileDialog class. It then opens the selected file using the StreamReader class and displays the text in the TextBox control:

   Private Sub mnuOpen_Click(ByVal sender As _
      System.Object, ByVal e As System.EventArgs) _
      Handles mnuOpen.Click
      Dim openFileDialog1 As New OpenFileDialog
      Dim sr As StreamReader
   
      openFileDialog1.InitialDirectory = "c:\"
      openFileDialog1.Filter = "txt files (*.txt)|*.txt"
      If openFileDialog1.ShowDialog() = _
         DialogResult.OK Then
         currentFilename = openFileDialog1.FileName
         StatusBar1.Text = currentFilename
         sr = New StreamReader( _
            openFileDialog1.FileName, _
            System.Text.Encoding.ASCII)
         TextBox1.Text = sr.ReadToEnd()
         sr.Close()
      End If
   End Sub

Similarly, the Save menu item calls the Save() method:

   Private Sub mnuSave_Click(ByVal sender As _
      System.Object, ByVal e As System.EventArgs) _
      Handles mnuSave.Click
   
      Save()
   End Sub

And the Save As… menu item calls the SaveAs() method:

   Private Sub mnuSaveAs_Click(ByVal sender As _
      System.Object, ByVal e As System.EventArgs) _
      Handles mnuSaveAs.Click
   
      SaveAs()
   End Sub

The SaveAs() method implementation uses the StreamWriter class to save the text in the TextBox control to a file. It prompts the user to enter a filename using the SaveFileDialog class:

   Public Sub SaveAs()
      Dim saveFileDialog1 As New SaveFileDialog
      Dim sw As StreamWriter
   
      saveFileDialog1.InitialDirectory = "\"
      saveFileDialog1.Filter = "txt files (*.txt)|*.txt"
      If saveFileDialog1.ShowDialog() = _
         DialogResult.OK Then
         currentFilename = saveFileDialog1.FileName
         StatusBar1.Text = currentFilename
         sw = New StreamWriter( _
            saveFileDialog1.FileName, True, _
            System.Text.Encoding.ASCII)
         sw.WriteLine(TextBox1.Text)
         sw.Close()
       End If
   End Sub

After saving a file, the application remembers the current filename using the global variable currentFilename.

The Save() method capitalizes on the saved file name by first checking to see if the currentFilename variable contains a filename. If not, the text has not been saved previously, and the code calls the SaveAs() method. If the currentFilename variable contains a filename but the file does not exist (perhaps the user has deleted it), the code also invokes the SaveAs() method. It then saves the file using the StreamWriter class:

   Public Sub Save()
      '---if no filename, invoke SaveAs()
      If currentFilename = "" Then
         SaveAs()
         Return
      End If
      '---if have filename, but file may not be there...
      If (Not File.Exists(currentFilename)) Then
         SaveAs()
         Return
      End If
   
      Dim sw As StreamWriter
      sw = New StreamWriter(currentFilename, False, _
         System.Text.Encoding.ASCII)
      sw.WriteLine(TextBox1.Text)
      sw.Close()
   End Sub

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