How to programmatically add hyperlinks to a Silverlight RichTextBox

There are many examples demonstrating how to embed hyperlinks into a Silverlight RichTextBox, but they all tend to be for design-time use.  This post discusses a technique for adding hyperlinks dynamically at runtime.

To begin, the following RichTextBox contains text from a Wikipedia article about Sir Edmund Hillary.

<UserControl

    x:Class="SilverlightApplication12.MainPage"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

    mc:Ignorable="d"

    d:DesignHeight="300"

    d:DesignWidth="400"

    >

    <Grid>

        <RichTextBox

            x:Name="rtb"

            Margin="10,10,10,10"

            IsReadOnly="True"

            FontFamily="Georgia"

            FontSize="16"

            TextAlignment="Justify"

            BorderThickness="0"

            >

            <Paragraph>

                <Run

                    FontStyle="Italic"

                    Text="&quot;Sir Edmund Percival Hillary, KG, ONZ, KBE (20 July 1919 – 11 January 2008) was a New Zealand mountaineer, explorer and philanthropist. On 29 May 1953, Hillary and Nepalese Sherpa mountaineer Tenzing Norgay became the first climbers confirmed as having reached the summit of Mount Everest – see Timeline of climbing Mount Everest. They were part of the ninth British expedition to Everest, led by John Hunt. He was named by Time magazine as one of the 100 most influential people of the 20th century.&quot;"

                    />

                <LineBreak />

                <LineBreak />

                <Run Text="from Edmund Hillary/Wikipedia"/>

                <LineBreak />

            </Paragraph>

        </RichTextBox>

    </Grid>

</UserControl>

Below, the developer is calling a custom extension method called “hyperlink” to add links to other Wikipedia articles. The key capability here is that hyperlinks are being added programmatically at runtime.

public partial class MainPage : UserControl {

    public MainPage() {

        InitializeComponent();

 

        this.rtb.Hyperlink("KG",
            "http://en.wikipedia.org/wiki/Order_of_the_Garter");

        this.rtb.Hyperlink("ONZ",
            "http://en.wikipedia.org/wiki/Order_of_New_Zealand");

        this.rtb.Hyperlink("KBE",
            "http://en.wikipedia.org/wiki/Order_of_the_British_Empire");

        this.rtb.Hyperlink("mountaineer",
            "http://en.wikipedia.org/wiki/Mountaineering");

        this.rtb.Hyperlink("Nepalese", "http://en.wikipedia.org/wiki/Nepal");

        this.rtb.Hyperlink("Sherpa", "http://en.wikipedia.org/wiki/Sherpa_people");

        this.rtb.Hyperlink("Tenzing Norgay",
            "http://en.wikipedia.org/wiki/Tenzing_Norgay");

        this.rtb.Hyperlink("Mount Everest",
            "http://en.wikipedia.org/wiki/Mount_Everest");

        this.rtb.Hyperlink("Timeline of climbing Mount Everest",
            "http://en.wikipedia.org/wiki/Timeline_of_climbing_Mount_Everest");

        this.rtb.Hyperlink("John Hunt",
            "http://en.wikipedia.org/wiki/John_Hunt,_Baron_Hunt");

        this.rtb.Hyperlink("100 most influential",
"http://en.wikipedia.org/wiki/Time_100:_The_Most_Important_People_of_the_Century");

        this.rtb.Hyperlink("Edmund Hillary",
            "http://en.wikipedia.org/wiki/Sir_Edmund_Hillary");

        this.rtb.Hyperlink("Wikipedia", "http://en.wikipedia.org");

    }

}

 

Below is the code that defines the "hyperlink” extension method used above.  After considerable research, I discovered that the best way to insert a hyperlink at runtime is to programmatically select text and then insert a hyperlink with the insert method.  The complication was, how to get a TextPointer  for the linked text?  Based on logic in last year’s article, I iterated through every Paragraph and Run until the searched text was found.  When the host Run was located, a TextPointer were extracted using the ContentStart and ContentEnd properties.

 

public static class Extensions {

    public static void Hyperlink(this RichTextBox rtb, string text, string link) {

        // Argument Checking

        if (string.IsNullOrWhiteSpace(text)) {

            throw new ArgumentNullException("text");

        }

        if (string.IsNullOrWhiteSpace(link)) {

            throw new ArgumentNullException("link");

        }

        if (!Uri.IsWellFormedUriString(link, UriKind.RelativeOrAbsolute)) {

            throw new ArgumentException("link is not a valid url");

        }

 

        foreach (Block block in rtb.Blocks) {

            Paragraph paragraph = block as Paragraph;

            if (paragraph == null){continue;}

            foreach (Inline inline in paragraph.Inlines) {

                Run run = inline as Run;

                if (run == null) { continue; }

                int index = run.Text.IndexOf(text);

                if (index == -1) { continue; }

 

                TextPointer start = run.ContentStart.GetPositionAtOffset(
                    index, LogicalDirection.Forward);

                TextPointer end = run.ContentStart.GetPositionAtOffset(
                    index + text.Length, LogicalDirection.Forward);

                rtb.Selection.Select(start, end);

 

                Hyperlink hyperlink = new Hyperlink() {

                    NavigateUri = new Uri(link),

                    TargetName = "_blank"

                };

                hyperlink.Inlines.Add(text);

                rtb.Selection.Insert(hyperlink);

                return;

            }

        }

    }

}

Silverlight’s RichTextBox is a very powerful control for rendering text with complicated formatting. This code makes it a little more powerful by adding the ability to dynamically add hyperlinks.

How to Encrypt/Decrypt Text in Silverlight/.NET

As web or application developers it is advisable to never transmit or store passwords as plain text. If unencrypted, a person could intentionally (or unintentionally) discover somebody else’s password. The technique described in this post is certainly not 100% secure but it makes password cracking difficult. To obtain a person’s original password the hacker must have the encrypted password and the key embedded in the client application.

The code included below will work in both Silverlight and .NET. An Advanced Encryption Standard (AES) symmetric algorithm is used to scramble/descramble text as shown in the screenshot above.

using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

using System.Windows;

 

namespace TestPasswordEncryption {

    public partial class MainWindow : Window {

        public MainWindow() {

            InitializeComponent();

 

            // Encrypt Text

            this.ButtonEncrypt.Click += (s, e) => {

                this.TextBoxEncrypted.Text =
                    Scrambler.Encrypt(this.TextBoxOriginal.Text);

            };

 

            // Decrypt Text

            this.ButtonDecrypt.Click += (s, e) => {

                this.TextBoxDecrypted.Text =
                    Scrambler.Decrypt(this.TextBoxEncrypted.Text);

            };

        }

    }

 

    internal class Scrambler {

        private const string PASS = "6D114A94-375E-4FFD-9F48-CF2C7A12620F";

        private const string SALT = "E5A8DB1B-5EAB-4C62-B322-CE24CE274303";

 

        internal static string Encrypt(string input) {

            // Test data

            byte[] utfdata = UTF8Encoding.UTF8.GetBytes(input);

            byte[] saltBytes = UTF8Encoding.UTF8.GetBytes(Scrambler.SALT);

 

            // We're using the PBKDF2 standard for password-based key generation

            Rfc2898DeriveBytes rfc = new Rfc2898DeriveBytes(

                Scrambler.PASS, saltBytes, 1000);

 

            // Our symmetric encryption algorithm

            AesManaged aes = new AesManaged();

            aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;

            aes.KeySize = aes.LegalKeySizes[0].MaxSize;

            aes.Key = rfc.GetBytes(aes.KeySize / 8);

            aes.IV = rfc.GetBytes(aes.BlockSize / 8);

 

            // Encryption

            ICryptoTransform encryptTransf = aes.CreateEncryptor();

 

            // Output stream, can be also a FileStream

            MemoryStream encryptStream = new MemoryStream();

            CryptoStream encryptor = new CryptoStream(

                encryptStream, encryptTransf, CryptoStreamMode.Write);

            encryptor.Write(utfdata, 0, utfdata.Length);

            encryptor.Flush();

            encryptor.Close();

 

            // Showing our encrypted content

            byte[] encryptBytes = encryptStream.ToArray();

            string encryptedString = Convert.ToBase64String(encryptBytes);

 

            // Close stream

            encryptStream.Close();

 

            // Return encrypted text

            return encryptedString;

        }

        internal static string Decrypt(string base64Input) {

            // Get inputs as bytes

            byte[] encryptBytes = Convert.FromBase64String(base64Input);

            byte[] saltBytes = Encoding.UTF8.GetBytes(Scrambler.SALT);

 

            // We're using the PBKDF2 standard for password-based key generation

            Rfc2898DeriveBytes rfc = new Rfc2898DeriveBytes(

                Scrambler.PASS, saltBytes);

 

            // Our symmetric encryption algorithm

            AesManaged aes = new AesManaged();

            aes.BlockSize = aes.LegalBlockSizes[0].MaxSize;

            aes.KeySize = aes.LegalKeySizes[0].MaxSize;

            aes.Key = rfc.GetBytes(aes.KeySize / 8);

            aes.IV = rfc.GetBytes(aes.BlockSize / 8);

 

            // Now, decryption

            ICryptoTransform decryptTrans = aes.CreateDecryptor();

 

            // Output stream, can be also a FileStream

            MemoryStream decryptStream = new MemoryStream();

            CryptoStream decryptor = new CryptoStream(

                decryptStream, decryptTrans, CryptoStreamMode.Write);

            decryptor.Write(encryptBytes, 0, encryptBytes.Length);

            decryptor.Flush();

            decryptor.Close();

 

            // Showing our decrypted content

            byte[] decryptBytes = decryptStream.ToArray();

            string decryptedString = UTF8Encoding.UTF8.GetString(

                decryptBytes, 0, decryptBytes.Length);

 

            // Close Stream

            decryptStream.Close();

 

            // Return decrypted text

            return decryptedString;

        }

    }

}