Load a web page using code behind

Question

I have a scenario where I am scraping some values out of one of my company intranet pages. I don't plan on showing the page in my app. I just need some of the data from the web page.

But I am noticing that a WebBrowser has to be created in Xaml for the LoadComplete event to fire. Since I am not going to show the webpage, I would rather not create it in Xaml.

Here is an Example that illustrates what I am talking about.

Xaml Version (the event fires fine):

Xaml:

<WebBrowser x:Name="webBrowser" Visibility="Collapsed"/>

Code:

public MainWindow() { InitializeComponent(); webBrowser.LoadCompleted += WebBrowserOnLoadCompleted; webBrowser.Navigate("http://stackoverflow.com/"); } private void WebBrowserOnLoadCompleted(object sender, NavigationEventArgs navArgs) { MessageBox.Show("PageLoaded"); }

Result: Then the MessageBox shows. (The event fires)

Code Only Version (The event does not fire):

Code:

public MainWindow() { InitializeComponent(); WebBrowser codeBehindBrowser = new WebBrowser(); codeBehindBrowser.LoadCompleted += WebBrowserOnLoadCompleted; codeBehindBrowser.Navigate("http://stackoverflow.com/"); } private void WebBrowserOnLoadCompleted(object sender, NavigationEventArgs navArgs) { MessageBox.Show("PageLoaded"); }

Result: The event does not fire.

Is there a way to get the event to fire if I make the WebBrowser in code behind?

VladL · Accepted Answer · 2013-03-06 23:14:51Z

3

If there is no need to show the page, you should better use the WebClient class

WebClient client = new WebClient(); //client.Credentials = new NetworkCredential("username", "password"); string reply = client.DownloadString(address);

There is also a DownloadStringAsync method, which will not block the UI

answered Mar 6, 2013 at 23:14

VladL

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2 Comments

Vaccano Over a year ago

This is a great way to get the data. But it comes back as a string. The rest of my code needs a IHTMLDocument2 to work with (or at least something I can search using xml). WebBrowser.Document can easily cast to IHTMLDocument2.

Vaccano Over a year ago

The HtmlAgilityPack let me query my data out using xpath. Thanks for the help! This works and is faster (because it is not rendering it)

Duncan Matheson · Accepted Answer · 2013-03-07 03:02:36Z

The reason the code-behind browser doesn't load is because it's not in the Visual Tree: it hasn't been put into the UI. The Xaml one works because it has been put into the Visual Tree, simply because it was created in Xaml.

If you want to create the browser from code then to get it to work you'll need to put it into the Visual Tree. For example:

<Window x:Class="WebBrowserLoadTest.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <Grid x:Name="LayoutRoot"/> </Window>

public MainWindow() { InitializeComponent(); WebBrowser codeBehindBrowser = new WebBrowser { Visibility = Visibility.Collapsed }; codeBehindBrowser.LoadCompleted += CodeBehindBrowserOnLoadCompleted; codeBehindBrowser.Navigate("http://stackoverflow.com/"); this.LayoutRoot.Children.Add(codeBehindBrowser); } private void CodeBehindBrowserOnLoadCompleted(object sender, NavigationEventArgs e) { MessageBox.Show("CodeBehindBrowser loaded, yay!"); }

As long as it's inserted into the Visual Tree somehow then it should work.

DotNetRussell · Accepted Answer · 2013-03-06 23:28:07Z

 MyWebClient client = new MyWebClient(); client.DownloadStringCompleted += new MyWebClient.DownloadStringCompletedEventHandler(HandleDownloadStringCompleted); // call the async method client.DownloadStringAsync(url, handler);

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