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Parsing URLs into Hyperlinks

It would be highly useful if long URLs written in a document gets automatically formatted into readable links. Parsing URLs into meaningful text in the document enhances its readability.


You can inculcate this parsing capability into standard RichTextbox control to provide seamless reading and writing experience to your users. The C1RichTextBox control is used in conjunction with C1TextParser library for the conversion. The C1TextParser library is a strong text parsing .NET library that enables you to convert and format URLs to hyperlinks automatically.


This enhancement in the standard RichTextBox control helps in creating more powerful and smart text editor.


Hyperlink Parsing


To create an application for parsing URLs into hyperlinks, follow these steps.

Set up the Application UI

  1. Create a new WPF App(.NET Framework) in Visual Studio.

  2. In the Solution Explorer, right-click Dependencies and select Manage NuGet Packages.

  3. In NuGet Package Manager, select nuget.org as the Package source.

  4. Search and install the following packages:

    • C1.XAML.WPF.RichTextbox

    • C1.TextParser

  5. In XAML view, add a RichTextbox control, a button control and a checkbox control in the grid by adding the following code inside the <Grid> tags.

    <Grid.RowDefinitions>
    <RowDefinition Height="1*"/>
    <RowDefinition Height="10*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
    <ColumnDefinition Width="5*"/>
    <ColumnDefinition Width="13*"/>
</Grid.ColumnDefinitions>
<Button x:Name="btnPasteDoc" Content="Paste Text with hyperlinks" Width="144" HorizontalAlignment="Left" Click="btnPasteDoc_Click" Grid.Row="0" Grid.Column="0" Margin="20,0,0,0"/>
<CheckBox Name="chkAutoConversion" Grid.Row="0" Grid.Column="1" Margin="23,3,7,7" Content="Allow Auto Hyperlink Conversion" FontSize="13" IsChecked="False" Checked="chkAutoConversion_Checked"/>
<c1:C1RichTextBox Name="smartRichTextBox" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" Margin="20,20,0,16" Height="200" Width="550" HorizontalAlignment="left" VerticalAlignment="Top"/>

  1. Add a class file in your application and named it as HyperlinkParser.cs.

  2. Declare the following IHyperlinkParser interface which contains two methods that are ExtractURLs and GetDisplayText.

    public interface IHyperlinkParser
{
    IEnumerable<string> ExtractURLs(string text);
    string GetDisplayText(string uri);
}
    Public Interface IHyperlinkParser
    Function ExtractURLs(text As String) As IEnumerable(Of String)
    Function GetDisplayText(uri As String) As String
End Interface

  3. Create a custom data extraction method named ExtractData to identify relevant portion of the text from a given text based on specific starting and ending criteria. In this method, the TextParser’s Starts-After-Continues-Until extractor extracts all the text present between StartsAfter/ContinuesUntil(Ends Before) text phrases.

    private List<ExtractedData> ExtractData(string text, string startsAfter, string continueUntil)
{
    //Extract URL from complete text
    var parser = new StartsAfterContinuesUntil(startsAfter, continueUntil);
    var result = parser.Extract(new MemoryStream(Encoding.UTF8.GetBytes(text)));
    //Create iObject by parsing the JSON string using Newtonsoft.Json.Linq.JObject.Parse
    var jObject = Newtonsoft.Json.Linq.JObject.Parse(result.ToJsonString());
    //Retrieves the value associated with the key "Result" from the JObject
    var jToken = jObject.GetValue("Result");
    //Convert jToken to a list of ExtractedData objects using jToken.ToObject<List<ExtractedData>>() 
    var extractedData = jToken.ToObject<List<ExtractedData>>();
    return extractedData;
}
    Private Function ExtractData(ByVal text As String, ByVal startsAfter As String, ByVal continueUntil As String) As List(Of ExtractedData)
    'Extract URL from complete text
    Dim parser = New StartsAfterContinuesUntil(startsAfter, continueUntil)
    Dim result = parser.Extract(New MemoryStream(Encoding.UTF8.GetBytes(text)))
    'Create iObject by parsing the JSON string using Newtonsoft.Json.Linq.JObject.Parse
    Dim jObject = Newtonsoft.Json.Linq.JObject.Parse(result.ToJsonString)
    'Retrieves the value associated with the key "Result" from the JObject
    Dim jToken = jObject.GetValue("Result")
    'Convert jToken to a list of ExtractedData objects using jToken.ToObject<List<ExtractedData>>() 
    Dim extractedData As List(Of ExtractedData) = jToken.ToObject(Of List(Of ExtractedData))()
    Return extractedData
End Function

  4. Define the ExtractURLs method to extract URLs from the given text. This method processes the input text to extract URLs that start with "http" or "https". It uses a custom data extraction method ExtractData to identify potential URL fragments, validates each URL using the Uri.IsWellFormedUriString method, and collects them into a list. The final list of valid URLs is then returned.

    public IEnumerable<string> ExtractURLs(string text)
{
    //Extract URLs starting with these protocols
    var _protocols = new List<string> { "http", "https" };
    List<string> urls = new List<string>();
    text += " ";
    foreach (var protocol in _protocols)
    {
        //extract the URL from the whole text
        var links = ExtractData(text, protocol, @"\s+");
        foreach (var link in links.Select(x => x.ExtractedText))
        {
            //if hyperlink is correct, add to list of URLs
            string hyperlink = $"{protocol}{link}";
            if (!Uri.IsWellFormedUriString(hyperlink, UriKind.Absolute))
                continue;
            if (!urls.Contains(hyperlink)) urls.Add(hyperlink);
        }
    }
    return urls;
}
    Public Function IHyperlinkParser_ExtractURLs(ByVal text As String) As IEnumerable(Of String) Implements IHyperlinkParser.ExtractURLs
    'Extract URLs starting with these protocols
    Dim _protocols As New List(Of String) From {"http", "https"}
    Dim urls As New List(Of String)()
    text &= " "
    For Each protocol In _protocols
        ' Extract the URL from the whole text
        Dim links = ExtractData(text, protocol, "\s+")
        For Each link In links.Select(Function(x) x.ExtractedText)
            ' If hyperlink is correct, add to list of URLs
            Dim hyperlink As String = $"{protocol}{link}"
            If Not Uri.IsWellFormedUriString(hyperlink, UriKind.Absolute) Then
                Continue For
            End If
            If Not urls.Contains(hyperlink) Then
                urls.Add(hyperlink)
            End If
        Next
    Next
    Return urls
End Function

  5. Create a method named ExtractDomainName(Uri uri) that takes a Uri object as input and returns the domain name as a string. This method extracts the domain name from a given URI by processing the host part of the URI. It then filters and selects the first non-empty extracted fragment as the domain name. If no valid domain name is found, it returns the original host.

    private string ExtractDomainName(Uri uri)
{
    IEnumerable<string> data = null;
    int dotCount = uri.Host.Count(x => x == '.');
    // This condition will be executed for extracting domain name if the uri host contains more than 1 dot('.'). 
    if (dotCount > 1)
        data = ExtractData(uri.Host, @"\.", @"\.").Select(x => x.ExtractedText);
    // This condition will be executed for extracting domain name if the uri host contains only one dot('.'). 
    if (dotCount == 1)
        data = ExtractData($" {uri.Host}", @" ", @"\.").Select(x => x.ExtractedText);
    var domainName = data.Where(x => !string.IsNullOrEmpty(x.Trim())).First();
    //return domain name
    return string.IsNullOrEmpty(domainName) ? uri.Host : domainName;
}
    Private Function ExtractDomainName(uri As Uri) As String
    Dim data As IEnumerable(Of String) = Nothing
    Dim dotCount As Integer = uri.Host.Count(Function(x) x = "."c)
    ' This condition will be executed for extracting domain name if the uri host contains more than 1 dot('.'). For example, www.google.com
    If dotCount > 1 Then
        data = ExtractData(uri.Host, "\.", "\.").Select(Function(x) x.ExtractedText)
    End If
    ' This condition will be executed for extracting domain name if the uri host contains only one dot('.'). For example, youtube.com
    If dotCount = 1 Then
        data = ExtractData($" {uri.Host}", " ", "\.").Select(Function(x) x.ExtractedText)
    End If
    Dim domainName As String = data.Where(Function(x) Not String.IsNullOrEmpty(x.Trim())).First()
    'return domain name
    Return If(String.IsNullOrEmpty(domainName), uri.Host, domainName)
End Function

  6. Create the method named ChooseDisplayText to filter out irrelevant segments, reverse the list to prioritize the most specific segments, and select the first valid segment as the display text. Then, format the selected text to title case and returns it. If the list of segments is empty, it returns an empty string.

    protected virtual string ChooseDisplayText(List<string> words)
{
    //get the correct words from the segments
    if (words.Count == 0) return string.Empty;
    string displayText = string.Empty;
    var correctWords = words.Where(x => !x.Equals("/")).ToList();
    if (correctWords.Count > 0)
    {
        //Choose the word to be used as display text for the hyperlink
        correctWords.Reverse();
        for (int index = 0; index < words.Count; index++)
        {
            displayText = $"{correctWords[index]}";
            break;
        }
    }
    //return the choosen word
    return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(displayText);
}
    Protected Overridable Function ChooseDisplayText(ByVal words As List(Of String)) As String
    'get the correct words from the segments
    If (words.Count = 0) Then
        Return String.Empty
    End If
    Dim displayText As String = String.Empty
    Dim correctWords = words.Where(Function(x) Not x.Equals("/")).ToList()
    If correctWords.Count > 0 Then
        ' Choose the word to be used as display text for the hyperlink
        correctWords.Reverse()
        For index As Integer = 0 To words.Count - 1
            displayText = $"{correctWords(index)}"
            Exit For
        Next
    End If
    'return the choosen word
    Return CultureInfo.CurrentCulture.TextInfo.ToTitleCase(displayText)
End Function

  7. Define the GetDisplayText(string uri) method to generate a user-friendly display text from a given URI. This method processes a given URI to generate a display-friendly text by extracting the domain name and URI segments, then using these parts to form a readable text. If any errors occur during the process, or if the generated display text is empty, the original URI is returned.

    public string GetDisplayText(string uri)
{
    try
    {
        //break URL into segments
        var uriObject = new Uri(uri);
        var words = new List<string>() { ExtractDomainName(uriObject) };
        words.AddRange(uriObject.Segments);
        //send these segments to get the choosen word for display
        var displayText = ChooseDisplayText(words);
        //return display text
        return string.IsNullOrEmpty(displayText) ? uri : displayText;
    }
    catch
    {
        //In case of errors, return whole URL
        return uri;
    }
}
    Public Function IHyperlinkParser_GetDisplayText(ByVal uri As String) As String Implements IHyperlinkParser.GetDisplayText
    Try
        'break URL into segments
        Dim uriObject = New Uri(uri)
        Dim words As New List(Of String) From {ExtractDomainName(uriObject)}
        words.AddRange(uriObject.Segments)
        'send these segments to get the choosen word for display
        Dim displayText = ChooseDisplayText(words)
        'return display text
        Return If(String.IsNullOrEmpty(displayText), uri, displayText)
        'TODO: Warning!!!, inline IF is not supported ?
        'TODO: Warning!!!! NULL EXPRESSION DETECTED...
    Catch
        'In case of errors, return whole URL
        Return uri
    End Try
End Function

  1. In the MainWindow.xaml.cs file, add the following code in the Click event of the Button control to paste some text in the RichTextBox control from Resources.resx file:

    private async void btnPasteDoc_Click(object sender, RoutedEventArgs e)
{
    //clear both textboxes
    smartRichTextBox.Text = string.Empty;
    //set document to clipboard
    var manager = new ResourceManager(@"SmartRichTextBox_NET48.Resources", Assembly.GetExecutingAssembly());
    Clipboard.SetText(manager.GetString("Document"), TextDataFormat.Text);
    await Task.Delay(50);
    smartRichTextBox.ClipboardPaste();
}
    Private Async Sub btnPasteDoc_Click(sender As Object, e As RoutedEventArgs)
    ' Clear both textboxes
    smartRichTextBox.Text = String.Empty
    ' Set document to clipboard
    Dim manager As New ResourceManager("SmartRichTextBox_NETFW_VB.Resourcesvb", Assembly.GetExecutingAssembly())
    Clipboard.SetText(manager.GetString("Document"), TextDataFormat.Text)
    Await Task.Delay(50)
    smartRichTextBox.ClipboardPaste()
End Sub

  2. Add the below code in the Checked event of the chkAutoConversion checkbox to display the textual links in the RichTextBox control in place of long URLs using the methods defined in the HyperlinkParser class. The methods are easily accessible using the object of the HyperlinkParser class.

    private void chkAutoConversion_Checked(object sender, RoutedEventArgs e)
{
    try
    {
        //Create parser object
        var hyperlinkParser = new HyperlinkParser();
        //Get pasted data from clipboard
        string text = Clipboard.GetText();
        //Converting hyperlinks into meaningful Text using methods of HyperlinkParser class
if (!string.IsNullOrEmpty(text))
        {
            var links = hyperlinkParser.ExtractURLs(text).ToList();
            foreach (var link in links)
            {
                var displayText = hyperlinkParser.GetDisplayText(link);
                var anchor = $"<a href={link}>{displayText}</a>";
                var pattern = $@"(^|\s){link}(\s|$)";
                Regex rgx = new Regex(pattern, RegexOptions.Compiled);
                text = rgx.Replace(text, $" {anchor} ");
            }
            Clipboard.SetData(DataFormats.Html, text);
            smartRichTextBox.Text = "";
            smartRichTextBox.ClipboardPaste();
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show($"{ex.Message}{Environment.NewLine}{ex.StackTrace}");
    }
}
    Private Sub chkAutoConversion_Checked(sender As Object, e As RoutedEventArgs)
    Try
        'Create parser object
        Dim hyperlinkParser As New HyperlinkParser()
        'Get pasted data from clipboard
        Dim text As String = Clipboard.GetText()
        'Converting hyperlinks into meaningful Text using methods of HyperlinkParser class
    If Not String.IsNullOrEmpty(text) Then
            Dim links As List(Of String) = hyperlinkParser.IHyperlinkParser_ExtractURLs(text).ToList()
            For Each link As String In links
                Dim displayText As String = hyperlinkParser.IHyperlinkParser_GetDisplayText(link)
                Dim anchor As String = $"<a href={link}>{displayText}</a>"
                Dim pattern As String = $"(^|\s){link}(\s|$)"
                Dim rgx As New Regex(pattern, RegexOptions.Compiled)
                text = rgx.Replace(text, $" {anchor} ")
            Next
            Clipboard.SetData(DataFormats.Html, text)
            smartRichTextBox.Text = ""
            smartRichTextBox.ClipboardPaste()
        End If
    Catch ex As Exception
        MessageBox.Show($"{ex.Message}{Environment.NewLine}{ex.StackTrace}")
    End Try
End Sub

  3. Execute the application and click the button control to paste some text in the RichTextBox control. Then, select the checkbox to convert the URLs into meaningful text in the RichTextBox.

Transforming a standard RichTextBox into a smart RichTextBox can greatly enhance user interaction and content creation efficiency.