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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

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