7.4 Displaying Message Boxes

You want to display a message to a user using a message box.

Technique

Use the static method Show defined within the MessageBox class. This method is overloaded several times, allowing you to customize the display of the message as you see fit. The simplest message box contains a single string parameter denoting the message to display. To add a caption to the message box, insert an additional string parameter. You can control which buttons are displayed in the third parameter by using the MessageBoxButtons enumerated data type. You can use a fourth parameter to display an icon. You specify this icon using a value from the MessageBoxIcon enumerated data type. To specify the default button, use a value from the MessageBoxDefaultButton enumerated data type as the fifth parameter. Finally, you specify additional options in the sixth parameter by using the logical or operator ( ) on values within the MessageBoxOptions enumeration. Table 7.1 shows the possible values for the enumerated data types discussed in this recipe.

Table 7.1. MessageBox Enumerated Data Types

Data Type	Value	Description
MessageBoxButtons	AbortRetryIgnore	Message box containing three buttons labeled Abort , Retry , and Ignore
	OK	A single button labeled OK
	OKCancel	Displays an OK button followed by a Cancel button
	RetryCancel	Shows two buttons labeled Retry and Cancel
	YesNo	Displays a Yes button and a No button
	YesNoCancel	Displays Yes , No , and Cancel buttons
MessageBoxIcon	Asterisk	Displays a lowercase i inside a circle in the corner of the message box
	Error	Icon is a white X inside a red circle
	Exclamation	Shows an exclamation point within a yellow triangle
	Hand	Shows same icon as Error value
	Information	Uses the same icon shown when using the Asterisk value
	None	Does not display an icon
	Question	Icon consists of a question mark within a circle
	Stop	Same as Error value, a white X inside a red circle
	Warning	Icon is the same as the Exclamation value
MessageBoxDefaultButton	Button1	Gives the first button the initial focus and renders a focus rectangle around the button
	Button2	Makes the second button, if one exists, the default button
	Button3	Makes the third button the default button
MessageBoxOptions	DefaultDesktopOnly	Displays the message box on the current desktop
	RightAlign	Aligns the text along the right edge of the message box
	RtlReading	Renders the text in the message box in right-to-left order
	ServiceNotification	Message box is displayed on the active desktop and will be shown even if a user is not logged on

Comments

Sometimes, all you need to do is display a simple message to the user or ask her a simple question. Message boxes handle this task, freeing you from having to create new forms. The MessageBox class contains a single static method, as well as the standard System.Object methods , named Show . There are 12 overloaded versions of this method corresponding to the level of customization you want to perform on the message box. In its most basic form, a message box can contain a single message and an OK button to close the message box. To show a message box with a single message, use the Show method with a single string parameter, and if you want to display a caption on the message box, create a second string parameter for that purpose:

 MessageBox.Show( "Simple Message Box" ); MessageBox.Show( "Simple Message Box", "With a caption" ); 

As mentioned earlier, you can customize the message box further by controlling the types of buttons and icons displayed, controlling which button is the default button, and specifying different message-box options. Based on the buttons that you elected to display on the message box, the value returned will be a value from the DialogResult enumerated data type. You can compare the value returned from the Show method with a value from the DialogResult type to determine the action performed by the user. The following code listing displays a message box using all the available customization options. Figure 7.2 shows the resulting message box:

 if( MessageBox.Show( "Simple Message Box",     "With a caption, default button, icon and RTL reading",     MessageBoxButtons.OKCancel,     MessageBoxIcon.Information,     MessageBoxDefaultButton.Button2,     MessageBoxOptions.RtlReading      MessageBoxOptions.RightAlign ) == DialogResult.Cancel )     {         return;     } 

Figure 7.2. The MessageBox.Show method contains several overloaded methods to customize the display of the message box.