apply bold, italic and underline to selected text in a richtextbox using visual basic.net - part 1

How To:

Apply Bold, Italic and Underline

Formatting to Selected Text in a .NET

RichTextBox (Part 1)

© DanieldotNET DEC2013

How to programmatically apply bold, italic or underline formatting to selected text

in a RichTextBox control.

Software Version: Visual Basic 2008 Express Edition, .NET 3.5

Contents

Introduction

The RichTextBox SelectionFont Property

Style Indicator Properties

Building the Demo Application

Coding the Buttons

Running the Demo Application

A Little Problem

Introduction

When creating a simple word processing application- which of course will

make use of the RichTextBox control – one may also want to include

common text formatting capabilities like Bold, Italic and Underline. Just how

this could be done is the subject of this two-part article.

The RichTextBox SelectionFont Property

This property in the RichTextBox control allows the programmer to retrieve,

or modify, the font of the highlighted text. When the font of a highlighted

text is modified, any other text typed immediately after the selected text will

also have the font applied to the previously selected text.

Using the RichTextBox.SelectionFont Property, the font style (Bold, Italic,

etc), the font size, and the font face of highlighted text within the control can

be modified. However, the only way to change the font style of the selected

text is to create a new font object. This is because the Style property of the

Font Class is ReadOnly – meaning once a Font object is created, there is no

way to change the style of the Font. If the text is to have another font style,

a new font object with the required style must be created.

The Style Indicator Properties

Once the Font object is constructed, it is possible to get information about

the style settings of the font. This is done by using the indicator properties

defined in the font object that correspond to each style. The table below

summarizes the Font style values defined in the FontStyle enumeration. The

FontStyle Enumeration is used by the Font class to specify style information

applied to text.

FontStyle Indicator Property Example

Regular None RichTextBox

Bold fontObject.Bold RichTextBox

Italic fontObject.Italic RichTextBox

Underline fontObject.Underline RichTextBox

Strikeout fontObject.Strikeout RichTextBox

An Indicator Property is a ReadOnly Boolean property defined in the Font

class that returns true if the specified style is set, otherwise it returns false.

For example, the indicator property for style bold is fontObject.Bold. if

fontObject has style Bold, calling fontObject.Bold will return True, otherwise

it will return False. Notice that FontStyle Regular has no corresponding

Indicator Function. To check if fontObject has the Regular style, all the other

indicators should be false.

Building the Demo Application

This Demo Application allows the user apply any of the three styles Bold, Italic or

Underline to highlighted text within a RichTextBox control. It can also toggle a Font

style off/on.

1. Create a new Windows Application named BoldItalicUnderline1.

2. Put three buttons and a RichTextBox control on Form1. Your interface

should resemble the one below.

3. Next, in the Properties Window, change the properties of the

controls as follows:

Button1 Text = Bold

Button2 Text = Italic

Button3 Text = Underline

RichTextBox1 Font.Size = 14

Form1 Text = Bold Italic Underline Demo 1

The interface should look like the following image

Coding the Demo

4. Now you can go to the Code Window and make your code to look like

the following one.

Visual Basic

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) _

Handles Button1.Click

' Check if the selected text is Boldened

If RichTextBox1.SelectionFont.Bold = True Then

' Change it to Regular Font

RichTextBox1.SelectionFont = _

New Font(RichTextBox1.SelectionFont, FontStyle.Regular)

Else

' Change it to Bold Font


New Font(RichTextBox1.SelectionFont, FontStyle.Bold)

End If

' Set input focus on the RichTextBox

RichTextBox1.Focus()

End Sub




' Check if the selected text is Italicized

If RichTextBox1.SelectionFont.Italic = True Then

' Change it to Regular font



Else

' Change it to Italic font


New Font(RichTextBox1.SelectionFont, FontStyle.Italic)

End If



End Sub




' Check if the selected text is Underlined

If RichTextBox1.SelectionFont.Underline = True Then

' Change it to Regular font



Else

' Change it to Underlined font


New Font(RichTextBox1.SelectionFont, FontStyle.Underline)

End If



End Sub

End Class

The event handling methods for buttons 1, 2 and 3 are similar, so the following

explanation applies for all three methods.

When the “Bold” button is clicked, the event handler first checks if the selected font

is Bold by using the following condition in the if-statement:

Visual Basic

RichTextBox1.SelectionFont.Bold = True

If it evaluates to “True”, it means that the selected text is bold. It then removes the

Bold formatting by applying a regular font style to it as shown below:

Visual Basic



On the other hand, if the selected text is not bold, it applies a bold formatting in a

way similar to the way it removed it. That is, by creating a new Font object having

the font style FontStyle.Bold

Visual Basic


New Font(RichTextBox1.SelectionFont, FontStyle.Bold)

Running the Demo

Press the F5 key to test the demo. Type any text into the RichTextBox. Then, select

any and apply the desired font style to it by clicking any of the buttons.

The figure shows the text

“The quick brown fox”

formatted as

“The quick brown fox”

To do it, select “quick” and press

button bold

Then, select “brown” and press

button italic

Finally, select the text “fox” and

press button underline

A Little Problem…

This demo only showed how to apply a single font style formatting to selected text

in a RichTextBox. However, the above demo cannot apply more than one font style

format to the selected text. Just try selecting any text and click bold. If italic is

clicked next, it cancels the bold formatting. Part 2 of this article will discuss how to

solve this problem.