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WPF HTML Supported TextBlock

, 7 Feb 2009
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This article describes HtmlTextBlock which is a WPF TextBlock that can parse a limited set of HTML tags and display them.
htmltextblock/mainscreen.jpg

Introduction

This article describes HtmlTextBlock which is a WPF TextBlock that can parse a limited set of HTML tags and display them.

Background

I was working on a custom progress dialog, which contains a Header, Message, Progress and some action buttons.

To make it look better, I want the message to support some text format, and I want it to be changeable at runtime, but it seems impossible using TextBlock.

htmltextblock/background.jpg

I then Googled how to use HTML in WPF but most solutions told me to use WebBrowser, which is a bit of an overkill for my purpose.

Then I remembered an abandoned project I wrote a few years ago (mostly because I moved to WPF) , which tried to recreate FlowDocument in .NET 2, and load HTML document (my main purpose, the component was named QzMiniHtml2).

Surprisingly, with very few modifications (mostly using import), this .NET 2 project worked nicely with WPF, just as you can see above.

Because of this, the original project is included as well.

How to Use?

The control is similar to TextBlock except you set the HTML property instead of Text.
Remember to use [ ] bracket instead of < >.

<Window x:Class="HtmlTextBlockTestProj.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:uc="http://www.quickzip.org/UserControls"
    Title="HtmlTextBlockTest" Height="250" Width="450">
    <DockPanel>
        <uc:HtmlTextBlock Html="{Binding Text, ElementName=tb}"
                 DockPanel.Dock="Top" Loaded="HtmlTextBlock_Loaded" />
        <TextBlock Text="[b] [i] [u] [a href=xx] [br] supported."
                 DockPanel.Dock="Bottom" />
        <TextBox TextWrapping="Wrap" AcceptsReturn="True"
                  VerticalScrollBarVisibility="Visible"
                  x:Name="tb"
        Text="The [i][u]quick brown fox[/i][/u] jumps over the [b]lazy dog[/b]" />
    </DockPanel>
</Window>         

How It Works?

The component actually included an HTML parsing engine inside, which translates HTML string to WPF's Bold, Italic, Underline, Hyperlink, LineBreak Inline (more can be added in future, you can do it yourself easily, see below.)

The conversion part is simple.

1) private Inline UpdateElement(HtmlTag aTag)
2) {
3)   Inline retVal = null;

4)   switch (aTag.Name)
5)   {
6)     case "text" :
7)       retVal = new Run(aTag["value"]);
8)       if (currentState.Bold) retVal = new Bold(retVal);
9)       if (currentState.Italic) retVal = new Italic(retVal);
0)       if (currentState.Underline) retVal = new Underline(retVal);
A)       break;
B)     case "br" :
C)       retVal = new LineBreak();
D)       break;
E)   }

F)   if (currentState.HyperLink != null && currentState.HyperLink != "")
G)   {
H)     Hyperlink link = new Hyperlink(retVal);
I)     link.NavigateUri = new Uri(currentState.HyperLink);
J)     retVal = link;
K)   }
L)    return retVal;
M) }         

First, please note that:

  • The input (aTag) is a Text or LineBreak(br), if the tag is a text, Tag["value"] is the text it holds.
    Bold, Italic, etc. can also be represented by HtmlTag, but they won't be executed here.
  • CurrentState holds the style affecting the TextTag, etc.

So if the tag is text (line 6):

  • it will generate a Run (which can contain format or unformat text, and unformat in this case) (line 7)
  • if it's bold, italic and underline, it will construct them, and using last Inline (Abstract class, Run, Bold, etc. inherited from it), so it contains the property.

When the Inline is returned (Line L):

  • It will be added to your HtmlTextBlock.Inlines collection.

History

  • 08-02-09 Initial version

License

This article, along with any associated source code and files, is licensed under The GNU Lesser General Public License (LGPLv3)

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Comments and Discussions

 
GeneralMy vote of 1 Pinmemberstarsky_chen6-Jan-13 5:16 
QuestionUnable to download the attached sample Pinmemberksvimalraj28-Jul-11 17:28 
AnswerRe: Unable to download the attached sample PinmemberLeung Yat Chun29-Jul-11 3:52 
GeneralSmall bug PinmemberArlenFeldman25-Mar-11 14:55 
GeneralThis is ... PinmemberXmen W.K.2-Jul-10 5:25 
GeneralSaving me a lot of time! PinmemberMember 324083012-Dec-09 5:01 
Generalimage in text block Pinmemberpathurun8-Sep-09 21:35 
Hi
Just wodnering if it is possible to display images also in Textblock.
Thanks.
GeneralRe: image in text block PinmemberLeung Yat Chun15-Sep-09 0:56 
GeneralDoes not work if Html Text is assigned to the HtmlTextBlock during Binding Pinmemberazamsharp1-Jul-09 10:09 
GeneralRe: Does not work if Html Text is assigned to the HtmlTextBlock during Binding PinmemberLeung Yat Chun2-Jul-09 7:06 
Generalextensions PinmemberLee_Nover20-Mar-09 15:11 
GeneralRe: extensions PinmemberLeung Yat Chun20-Mar-09 20:35 
GeneralRe: extensions PinmemberLee_Nover23-Mar-09 4:14 
GeneralRe: extensions PinmemberLeung Yat Chun23-Mar-09 10:20 
GeneralRe: extensions PinmemberLee_Nover24-Mar-09 3:45 
GeneralRe: extensions PinmemberLeung Yat Chun25-Mar-09 9:20 
GeneralRe: extensions PinmemberBob Ranck4-Apr-09 9:26 
GeneralRe: extensions PinmemberLeung Yat Chun5-Apr-09 20:45 
QuestionFlow document? PinmemberMember 17809897-Feb-09 21:32 
AnswerRe: Flow document? PinmemberLeung Yat Chun7-Feb-09 22:39 
GeneralRe: Flow document? PinmemberMember 17809898-Feb-09 22:38 
GeneralRe: Flow document? PinmemberLeung Yat Chun9-Feb-09 9:04 

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