Apply Bold, Italic and Underline to Selected Text in a RichtextBox using Visual Basic.Net - Part 1
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1) The document discusses how to programmatically apply bold, italic, and underline formatting to selected text in a .NET RichTextBox control. 2) It describes using the RichTextBox's SelectionFont property to modify the font of highlighted text, and creating new font objects to change the style since the Style property of the Font class is read-only. 3) A demo application is built to allow applying bold, italic, or underline styles to selected text and toggle styles on/off, but it is noted this application cannot apply multiple font styles simultaneously.
Apply Bold, Italic and Underline to Selected Text in a RichtextBox using Visual Basic.Net - Part 1
- 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
- 2. 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. 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
- 4. Coding the Demo 4. Now you can go to the Code Window and make your code to look like the following one.
- 5. 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 RichTextBox1.SelectionFont = _ New Font(RichTextBox1.SelectionFont, FontStyle.Bold) End If ' Set input focus on the RichTextBox RichTextBox1.Focus() End Sub Private Sub Button2_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button2.Click ' Check if the selected text is Italicized If RichTextBox1.SelectionFont.Italic = True Then ' Change it to Regular font RichTextBox1.SelectionFont = _ New Font(RichTextBox1.SelectionFont, FontStyle.Regular) Else ' Change it to Italic font RichTextBox1.SelectionFont = _ New Font(RichTextBox1.SelectionFont, FontStyle.Italic) End If ' Set input focus on the RichTextBox RichTextBox1.Focus() End Sub
- 6. Private Sub Button3_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button3.Click ' Check if the selected text is Underlined If RichTextBox1.SelectionFont.Underline = True Then ' Change it to Regular font RichTextBox1.SelectionFont = _ New Font(RichTextBox1.SelectionFont, FontStyle.Regular) Else ' Change it to Underlined font RichTextBox1.SelectionFont = _ New Font(RichTextBox1.SelectionFont, FontStyle.Underline) End If ' Set input focus on the RichTextBox RichTextBox1.Focus() 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 RichTextBox1.SelectionFont = _ New Font(RichTextBox1.SelectionFont, FontStyle.Regular) 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
- 7. Visual Basic RichTextBox1.SelectionFont = _ 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.