Skip to main content

Binding a HTML-formatted string to a WPF WebBrowser control

Sometimes there is a need to display a HTML formatted string in a WPF application. There are a couple of ways to do this, but the most stright forward is to use a WebBrowser control and the NavigateToString method.

This approach has one big flaw, you cannot use binding to a string out of the box, but I found a great solution through Stack Overflow which adds a bindable property to the  WebBrowser control using  NavigateToString.

The following class is all that is needed to add that behavior. A new depencency property named Html is introduced to the  WebBrowser and the proper change action is performed in the OnHtmlChanged method.

public class BrowserBehavior
{
    public static readonly DependencyProperty HtmlProperty = DependencyProperty.RegisterAttached(
        "Html", typeof(string), typeof(BrowserBehavior), new FrameworkPropertyMetadata(OnHtmlChanged));

    [AttachedPropertyBrowsableForType(typeof(WebBrowser))]
    public static string GetHtml(WebBrowser browser)
    {
        return (string)browser.GetValue(HtmlProperty);
    }

    public static void SetHtml(WebBrowser browser, string value)
    {
        browser.SetValue(HtmlProperty, value);
    }

    static void OnHtmlChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
    {
        var browser = dependencyObject as WebBrowser;
        if (browser != null)
        {
            browser.NavigateToString(e.NewValue);
        }
    }
}

To bind this property the XAML looks like this:
<WebBrowser local:BrowserBehavior.Html="{Binding Path=HtmlText}"></WebBrowser>

Since we are printing some swedish characters the encoding got a little bit funky. This is nothing that the  WebBrowser control itself affects, but it has to be set with an encoding meta tag in the HTML. So simply add the following meta tag to the head section of the HTML to be shown in the browser control:
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />

Another thing that does not seem to be able to affect on the  WebBrowser control is the context menu. The default context menu is the same as you would get in an Internet Explorer window. When using the  NavigateToString method to add the content the navigation in the browser control will not work. Hence we would like to hide the context menu. The easiest way to do so is with a litte javascript in the rendered HTML:
<body oncontextmenu="return false;">

By adding these little hacks we have an easy way to show HTML content in a bindable fashion. Sure there are still some caveats to this solution, for instance an F5 keystroke will refresh the browser window. But we cannot use WebBrowserShortcutsEnabled since we want the users to be able to copy text from the browser using the Ctrl-C shortcut.

Comments

  1. Does not make sense if you are reading it and you want start from scratch.
    Does not show what components have to be implemented.
    Actually , looking for solution how to make some kind of html viewer that points to html file make works ( of course I can read the html file to string variable )
    For instance " browser.NavigateToString(e.NewValue);"
    I tried browser.NavigateToString((string)e.NewValue);

    ReplyDelete

Post a Comment

Popular posts from this blog

Moving to the cloud - part 1

I cannot with words describe the hype around the cloud today, and of course I had to join the croud. I have transferred all my applications, files and services to the cloud. I thought I would share some of the experiences and difficulties I have hit during my jourey. These are the steps I have performed in order to complete my move to the cloud: Most of my files are safely stored with  Dropbox . E-mail accounts for stodell.se  were moved from service provider to  Google Apps . The Cornball was moved from service provider to  Windows Azure och SQL Azure . This blog was moved from Wordpress at a service provider to  Google's Blogger . Even though  Loopia has been a great service provider during many years I have now been able to cancel all my services except the domain hosting with them. The replacement being free services and the Azure capacity that is included in the MSDN subscription.

Using Bootstrap Tooltip to show Parsley validation errors

I'm currently working on a web application using a variety of different frameworks, such as Backbone for the back-end, Bootstrap for the front-end and Parsley for client side form validation.  Parsley is a really powerful validation toolkit, but it takes some tweaking to make it blend with the Bootstrap front-end. Fortunately this is a one time fix, which can be re-used all over our project. Since there will be some custom options in our  Parsley  object, we can't use the default parsley-validate attribute on the form. Instead we have to initialize the validation with the jQuery syntax: $('#my-form').parsley(parsleyOptions); The options are were the magic happens, and in our case we have a global options object that our forms use to get the same experience all over the application. Here's what it looks like: var parsleyOptions = {  // Sets success and error class to Bootstrap class names  successClass: 'has-success',  errorClass: 'has-er