To change the appearance of the text inside a RichTextBox, you first select the text that you want to change, and then you set one of the control's properties to modify the text.

To select the text, you use the control's SelectionStart and SelectionLength properties to indicate where the text begins and how many letters it includes. Note that the letters are numbered starting with 0. (In fact, almost all numbering starts with 0 in Visual Basic.) For example, setting SelectionStart = 0 and SelectionLength = 1 selects the control's first letter.

After you select the text, you set one of the RichTextBox's properties to the value that you want the text to have.

For example, the following code makes the RichTextBox named rchContent display some text and color the word "red":

rchContent.Text = "Some red text"
rchContent.SelectionStart = 5
rchContent.SelectionLength = 3
rchContent.SelectionColor = Color.Red

Table 7-1 lists properties that you can use to change the text's appearance.

The FontFeatures example program shown in Figure 7-1 demonstrates properties that change the appearance of text within a paragraph. These include the SelectionBackColor, SelectionCharOffset, SelectionColor, and SelectionFont.

Figure 7.1. FIGURE 7-1

Figure 7.2. FIGURE 7-2

The ParagraphFeatures program shown in Figure 7-2 demonstrates properties that change the way paragraphs are displayed. These include SelectionIndent, SelectionHangingIndent, SelectionRightIndent, SelectionBullet, and SelectionAlignment.

Table 7-2 summarizes four additional properties that change the text displayed by the control that deserve special mention.

Allowing the user to change text settings is easy. When the user selects text in the control, the RichTextBox sets its SelectionStart and SelectionLength properties accordingly. All you need to do is set the appropriate property (for example, SelectionColor) and the selected text is updated.

The SetTextProperties example program shown in Figure 7-3 (and available as part of the Lesson 7 code download) uses this technique to let the user control text color, character offset, and paragraph alignment. Select text and then click the tool strip buttons to change the text's properties.

Figure 7.3. FIGURE 7-3

The following code shows how the program changes the currently selected text to have a black background and white foreground:

Private Sub btnReversedColors_Click() Handles btnReversedColors.Click
    rchContent.SelectionColor = Color.White

rchContent.SelectionBackColor = Color.Black
End Sub

The program's other buttons work similarly.

Lesson 2 briefly described properties, methods, and events. Other lessons have also worked with many properties and events. In fact, most of the event handlers I've discussed in the lessons so far catch an event and change a property in response.

Though you've worked with many properties and events, the only method you've seen is the form's Close method, which makes the form go away. For example, the following code closes the form that executes it:

Me.Close()

The RichTextBox provides many new methods that are helpful for building a text editing program. Table 7-3 summarizes some of the most useful.

The following code shows how a program can use the LoadFile method. The first parameter gives the name of the file, which can be relative to the program's current directory or a full path. The second parameter gives the type of file.

rchContent.LoadFile("Test.rtf", RichTextBoxStreamType.RichText)

TYPING TIPS

When you type rchContent.LoadFile, IntelliSense displays a popup showing the parameters that the LoadFile method expects, as shown in Figure 7-4.

Figure 7.4. FIGURE 7-4

There are several different overloaded versions of the method to choose from. Overloaded versions of a method have the same name but take different parameters.

Use the up and down arrow keys to scroll through the method's available versions.

As you enter parameters, IntelliSense updates to describe the next parameter that it expects. For example, after you enter a filename, IntelliSense updates to indicate that it expects a file type next.

The following code shows how a program can use the SaveFile method. As with LoadFile, the first parameter gives the file's name and the second gives its type.

rchContent.SaveFile("Test.rtf", RichTextBoxStreamType.RichText)

In this Try It, you add functionality to some of the SimpleEdit program's menu items and tool strip buttons. You use the RichTextBox properties and methods to implement the commands in the Edit menu: Undo, Redo, Copy, Cut, Paste, Delete, and Select All. (This also makes the corresponding buttons work at no extra charge.)