I need to create an WPF app in which I'm showing text that is scraped from a site. In every new day, the text is changed. Nevertheless, the problem is that this text contains hyperlinks, and I need to scrape them also. In this sense, I am scraping the innerHtml and modifying to be readable to XAML.

Suppose I am scraping this HTML:

<p>Click <a href="google.com"> here </a> !!</p>

I modify this to be readable to XAML like this:

<TextBlock> Click <Hyperlink RequestNavigate=\"Hyperlink_RequestNavigate\" NavigateUri='https://www.google.com/'> here </Hyperlink> !!! </TextBlock>

How am I doing this?

public partial class MainWindow : Window
{    
    public MainWindow()
    {
        InitializeComponent();
        var str = " Click <Hyperlink RequestNavigate=\"Hyperlink_RequestNavigate\" NavigateUri='https://www.google.com/'> here </Hyperlink> !!! ";
        grid.Children.Add(CreateTextBlock(str));
    }

    public TextBlock CreateTextBlock(string inlines)
    {
        var xaml = "<TextBlock xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">"
              inlines   "</TextBlock>";
        return XamlReader.Parse(xaml) as TextBlock;
    }

    public void Hyperlink_RequestNavigate(object sender, RequestNavigateEventArgs e)
    {
        Process.Start(new ProcessStartInfo(e.Uri.AbsoluteUri) { UseShellExecute = true });
        e.Handled = true;
    }
}

All good until now, but the error above comes in:

System.Windows.Markup.XamlParseException: ''Failed to create a 'RequestNavigate' from the text 'Hyperlink_RequestNavigate'.' ArgumentException: Cannot bind to the target method because its signature is not compatible with that of the delegate type.

Thank you for the help.

CodePudding user response：

The XamlReader.Parse() will not allow dynamically attach the RequestNavigate event handler this way. But you can do the following:

• Add a name to the Hyperlink.
• Load/Parse the XAML without RequestNavigate.
• Add the RequestNavigate event handler programmatically.

public MainWindow()
{
    InitializeComponent();

    var str = " Click <Hyperlink Name=\"hyperName\" NavigateUri=\"https://www.google.com/\"> here </Hyperlink> !!! ";
    grid.Children.Add(CreateTextBlock(str));
}

public TextBlock CreateTextBlock(string inlines)
{
    var xaml = "<TextBlock xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">"   inlines   "</TextBlock>";
    var tb = XamlReader.Parse(xaml) as TextBlock;                
    if (tb != null && tb.FindName("hyperName") is Hyperlink hyperln)
    {
        hyperln.RequestNavigate  = Hyperlink_RequestNavigate;
    }
    return tb;
}

public void Hyperlink_RequestNavigate(object sender, RequestNavigateEventArgs e)
{
    ...
}

CodePudding user response：

The XamlReader.Parse method doesn't support event handlers but you could simply remove RequestNavigate="Hyperlink_RequestNavigate" from the XAML being parsed and handle the RequestNavigate event for all hyperlinks by attaching an event handler for the routed event to the Grid:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        var str = " Click <Hyperlink NavigateUri='https://www.google.com/'> here </Hyperlink> !!! ";
        grid.Children.Add(CreateTextBlock(str));
        grid.AddHandler(Hyperlink.RequestNavigateEvent, new RequestNavigateEventHandler(Hyperlink_RequestNavigate));
    }

    public TextBlock CreateTextBlock(string inlines)
    {
        var xaml = "<TextBlock xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">"
              inlines   "</TextBlock>";
        return XamlReader.Parse(xaml) as TextBlock;
    }

    public void Hyperlink_RequestNavigate(object sender, RequestNavigateEventArgs e)
    {
        Process.Start(new ProcessStartInfo(e.Uri.AbsoluteUri) { UseShellExecute = true });
        e.Handled = true;
    }
}