458 Part IV Working with Windows Applications

Handling Menu Events

The menu that you have built so far looks very pretty, but none of the items do anything when you click them. To make them functional, you have to write code to handle the various

menu events. Several different events can occur when a user selects a menu item. Some are more useful than others are. The most frequently used event is the Click event, which oc-

curs when the user clicks the menu item. You typically trap this event to perform the tasks associated with the menu item.

In the following exercise, you will learn more about menu events and how to process them. You will create Click events for the newMember and exit menu items.

The purpose of the New Member command is so that the user can enter the details of a new member. Therefore, until the user clicks New Member, all fields on the form should be disabled, as should the Save Member Details command. When the user clicks the New Member

command, you want to enable all the fields, reset the contents of the form so that the user can start adding information about a new member, and enable the Save Member Details

command.

Handle the and menu item events

1.In the XAML pane, click the definition of the firstName text box. In the Properties window, clear the IsEnabled property. (This action sets IsEnabled to False in the XAML definition.)

Repeat this process for the lastName, towerNames, isCaptain, hostMemberSince, yearsExperience, methods, add, and clear controls and for the saveMember menu item.

2.In the Design View window, in the XAML pane, begin entering the code shown here in bold type in the XAML description of the _New Member menu item:

<MenuItem Header=”_New Member” Click=”>

3.When the shortcut menu appears after you type the opening quotation mark, double-click the <New Event Handler> command.

Visual Studio generates an event method called newMember_Click and associates it with the Click event for the menu item.

Tip Always give a menu item a meaningful name when you define event methods for it. If you don’t, Visual Studio generates an event method called MenuItem_Click for the Click event. If you then create Click event methods for other menu items that also don’t have names, they are called MenuItem_Click_1, MenuItem_Click_2, and so on. If you have several

of these event methods, it can be difficult to work out which event method belongs to which menu item.

4.Switch to the Code and Text Editor window displaying the Window1.xaml.cs file. (On the View menu, click Code.)

The newMember_Click event method will have been added to the bottom of the Window1 class definition:

private void newMember_Click(object sender, RoutedEventArgs e)

{

}

5. Add the following statements shown in bold type to the memberFormClosing method:

private void newMember_Click(object sender, RoutedEventArgs e)

{

this.Reset(); saveMember.IsEnabled = true; firstName.IsEnabled = true; lastName.IsEnabled = true; towerNames.IsEnabled = true; isCaptain.IsEnabled = true; hostMemberSince.IsEnabled = true; yearsExperience.IsEnabled = true; methods.IsEnabled = true; add.IsEnabled = true; clear.IsEnabled = true;

}

This code calls the Reset method and then enables all the controls. If you remember from Chapter 22, the Reset method resets the controls on the form to their default values. (If you don’t recall how the Reset method works, scroll the Code and Text Editor

window to display the method and refresh your memory.)

Next, you need to create a Click event method for the Exit command. This method should cause the form to close.

6.Return to the Design View window displaying the Window1.xaml file. Use the technique you followed in step 2 to create a Click event method for the exit menu item called exit_Click.

7.Switch to the Code and Text Editor window. In the body of the exitClick method, type the statement shown in bold type in the following code:

private void newMember_Click(object sender, RoutedEventArgs e)

{

this.Close();

}

The Close method of a form attempts to close the form. Remember that if the form intercepts the Closing event, it can prevent the form from closing. The Middleshire

Bell Ringers Association application does precisely this, and it asks the user if he or she wants to quit. If the user says no, the form does not close and the application continues to run.

460 Part IV Working with Windows Applications

The next step is to handle the saveMember menu item. When the user clicks this menu item, the data on the form should be saved to a file. For the time being, you will save the information to an ordinary text file called Members.txt in the current folder. Later, you will modify the code so that the user can select an alternative file name and location.

Handle the menu item event

1.Return to the Design View window displaying the Window1.xaml file. In the XAML pane, locate the definition of the saveMember menu item and use the <New Event Handler> command to specify a Click event method called saveMember_Click. (This is the default name generated by the <New Event Handler> command.)

2.In the Code and Text Editor window displaying the Window1.xaml.cs file, scroll to the top of the file and add the following using statement to the list:

using System.IO;

3.Locate the saveMember_Click event method at the end of the file. Add the following statements shown in bold type to the body of the method:

private void saveMember_Click(object sender, RoutedEventArgs e)

{

using (StreamWriter writer = new StreamWriter(“Members.txt”))

{

writer.WriteLine(“First Name: {0}”, firstName.Text); writer.WriteLine(“Last Name: {0}”, lastName.Text); writer.WriteLine(“Tower: {0}”, towerNames.Text); writer.WriteLine(“Captain: {0}”, isCaptain.IsChecked.ToString()); System.Windows.Forms.DateTimePicker memberDate =

hostMemberSince.Child as System.Windows.Forms.DateTimePicker; writer.WriteLine(“Member Since: {0}”, memberDate.Value.ToString()); writer.WriteLine(“Methods: “);

foreach (CheckBox cb in methods.Items)

{

if (cb.IsChecked.Value)

{

writer.WriteLine(cb.Content.ToString());

}

}

MessageBox.Show(“Member details saved”, “Saved”);

}

}

This block of code creates a StreamWriter object that the method uses for writing text to the Member.txt file. Using the StreamWriter class is very similar to displaying text in a console application by using the Console object—you can simply use the WriteLine

method.

When the details have all been written out, a message box is displayed giving the user some feedback (always a good idea).

4.The Add button and its associated event method are now obsolete, so in the Design View window delete the Add button. In the Code and Text Editor window, comment out the add_Click method.

5.In the newMember_Click method, comment out the following statement:

// add.IsEnabled = true;

The remaining menu item is the about menu item, which should display a dialog box providing information about the version of the application, the publisher, and any other useful information. You will add an event method to handle this event in the next exercise.

Handle the menu item event

1.On the Project menu, click Add Window.

2.In the Add New Item – BellRingers dialog box, in the Templates pane, click Window (WPF). In the Name text box, type About.xaml, and then click Add.

When you have added the appropriate controls, you will display this window when the user clicks the About Middleshire Bell Ringers command on the Help menu.

Note Visual Studio provides the About Box windows template. However, this template generates a Windows Forms window rather than a WPF window.

3.In the Design View window, click the About.xaml form. In the Properties window, change the Title property to About Middleshire Bell Ringers, set the Width property to 300, and set the Height property to 156. Set the ResizeMode property to NoResize to prevent the user from changing the size of the window.

4.In the Name box at the top of the Properties window, type AboutBellRingers.

5.Add two label controls and a button control to the form. In the XAML pane, modify the

properties of these three controls as shown here in bold type (feel free to change the text displayed by the buildDate label if you prefer):

<Window x:Class=”BellRingers.About” xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation” xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml” Title=”About Middleshire Bell Ringers” Height=”156” Width=”300”

Name=”AboutBellRingers” ResizeMode=”NoResize”> <Grid>

<Label Margin=”80,20,0,0” Name=”version” Height=”30” VerticalAlignment=”Top” HorizontalAlignment=”Left” Width=”75”>Version 1.0</Label>

Test the menu events

1.On the Debug menu, click Start Without Debugging to build and run the application. Notice that all the fields on the form are disabled.

2.Click the File menu.

The Save Member Details command is disabled.

3.On the File menu, click New Member. The fields on the form are now available.

4.Input some details for a new member.

5.Click the File menu again.

The Save Member Details command is now available.

6.On the File menu, click Save Member Details.

After a short delay, the message “Member details saved” appears. Click OK in this message box.

7.Using Windows Explorer, move to the \Microsoft Press\Visual CSharp Step by Step\ Chapter 23\BellRingers\BellRingers\bin\Debug folder under your Documents folder.

You should see a file called Members.txt in this folder.

8.Double-click Members.txt to display its contents using Notepad. This file should contain the details of the new member.

9.Close Notepad, and return to the Middleshire Bell Ringers application.

10.On the Help menu, click About Middleshire Bell Ringers.

The About window appears. Notice that you cannot resize this window, and you cannot click any items on the Members form while the About window is still visible.

11.Click OK to return to the Members form.

12.On the File menu, click Exit.

The form tries to close. You are asked if you are sure you want to close the form. If you click No, the form remains open; if you click Yes, the form closes and the application finishes.

13.Click Yes to close the form.