C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Documents;
using Word = Microsoft.Office.Interop.Word;

namespace Schweinelatein
{
    /// <summary>
    /// Interaktionslogik für MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        Word.Application app;
        public MainWindow()
        {
            InitializeComponent();
            app = new Word.Application();
            textblockNToPig.Text = "\u2193 Übersetzen \u2193";
            textblockPigToN.Text = "\u2191 Übersetzen \u2191";
        }

        public string CreatePigLatin(string original, string pig)//Neues Wort erstellen, pig ist die Silbe
        {
            if (string.IsNullOrEmpty(original))
            {
                return null;
            }
            int i = original.Length;
            char konsonant = original.First(x => !(x != 'a' && x != 'e' && x != 'i' && x != 'o' && x != 'u' && x != 'ä' && x != 'ö' && x != 'ü' && x != '\0' && x != 'A' && x != 'E' && x != 'I' && x != 'O' && x != 'U' && x != 'Ä' && x != 'Ö' && x != 'Ü'));
            int index = original.IndexOf(konsonant);
            if (index > 0)
            {
                string cut = original.Substring(0, index).ToLower();
                string rest = original.Substring(index, original.Length - index);
                if (char.IsUpper(original[0]))
                {
                    rest = original.Substring(index, 1).ToUpper() + original.Substring(index + 1, original.Length - index - 1);
                }
                return rest + cut + pig;
            }
            else
            {
                return original + pig;
            }
        }

        public string CreatePigText(string original, string pig = "ay")//Erstelle für alle Wörter ein neues "Schweinewort"
        {
            List<KeyValuePair<string, char>> split = GotSplittedAt(original, ' ', ',', '!', '.', '=', '?', ';', '\r', '\n', '\t', '\0', '\"', '„', '“');
            string Out = null;
            foreach (KeyValuePair<string, char> el in split)
            {
                Out += CreatePigLatin(el.Key, pig) + el.Value;
            }
            Out = Out.Substring(0, Out.Length - 1);
            return Out;
        }

        public string CreateNormalText(string pigLatin, string pig)//Erstellt den Ursprungstext
        {
            List<KeyValuePair<string, char>> split = GotSplittedAt(pigLatin, ' ', ',', '!', '.', '=', '?', ';', '\r', '\n', '\t', '\0', '\"', '„', '“');
            string Out = null;
            foreach (KeyValuePair<string, char> el in split)
            {
                Out += CreateNormalWord(el.Key, pig) + el.Value;
            }
            Out = Out.Substring(0, Out.Length - 1);
            return Out;
        }

        public string GetCorrectWord(string pigLatin)//Findet das ursprüngliche Wort heraus, ohne Silbe
        {
            /*
            piglatin:   Schwein --> Einschway
            mögliche Wörter:
            Einschw
            Weinsch
            Hweinsc
            Chweins
            Schwein
            ...
            
            Das einzig tatsächlich existierende Wort ist Schwein,
            das auch zurückgegeben wird.
            */

            string text = pigLatin;
            bool isUpper = char.IsUpper(pigLatin[0]);
            List<string> words = new List<string>();
            for (int i = 0; i != pigLatin.Length; i++)
            {
                string word = text;
                if (isUpper)
                {
                    word = text.Substring(0, 1).ToUpper() + text.Substring(1, text.Length - 1).ToLower();
                }
                words.Add(word);
                text = text.Substring(text.Length - 1, 1) + text.Substring(0, text.Length - 1);
            }

            List<bool> correct = CheckSpelling(words).ToList();
            try
            {
                return words[correct.IndexOf(true)];
            }
            catch
            {
                return string.Format("%Error:[ {0} ]%", pigLatin);
            }
        }

        public string CreateNormalWord(string pigLatin, string pig)//Normales Wort aus Schweinelatein erstellen, pig ist die Silbe
        {
            if (!string.IsNullOrEmpty(pigLatin))
            {
                if (pigLatin.EndsWith(pig))
                {
                    string temp = pigLatin.Substring(0, pigLatin.Length - pig.Length);
                    return GetCorrectWord(temp);
                }
                else
                { return string.Format("%Error:[ {0} ]%", pigLatin); }
            }

            return null;
        }

        public IEnumerable<bool> CheckSpelling(IEnumerable<string> words)//Rechtschreibung prüfen
        {
            foreach (string word in words)
            {
                yield return app.CheckSpelling(word);
            }
        }

        public List<KeyValuePair<string, char>> GotSplittedAt(string Text, params char[] seperator)
        {
            List<KeyValuePair<string, char>> split = new List<KeyValuePair<string, char>>();
            char[] temp = Text.ToCharArray();
            string part = null;
            foreach (char el in temp)
            {
                if (!seperator.Contains(el))
                {
                    part += Convert.ToString(el);
                }
                else
                {
                    split.Add(new KeyValuePair<string, char>(part, el));
                    part = null;
                }
            }
            split.Add(new KeyValuePair<string, char>(part, '\0'));
            return split;
        }

        private void buttonTranslateNToPig_Click(object sender, RoutedEventArgs e)
        {
            string orig = new TextRange(richTextBoxOrig.Document.ContentStart, richTextBoxOrig.Document.ContentEnd).Text;
            string text = CreatePigText(orig, textBoxKey.Text);
            richTextBoxPig.Document.Blocks.Clear();
            richTextBoxPig.Document.Blocks.Add(new Paragraph(new Run(text)));
        }

        private void buttonTranslatePigToN_Click(object sender, RoutedEventArgs e)
        {
            string pig = new TextRange(richTextBoxPig.Document.ContentStart, richTextBoxPig.Document.ContentEnd).Text;
            string text = CreateNormalText(pig, textBoxKey.Text);
            richTextBoxOrig.Document.Blocks.Clear();
            richTextBoxOrig.Document.Blocks.Add(new Paragraph(new Run(text)));
        }

        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            app.Quit();
        }
    }
}

XML-Code

<Window
        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"
        xmlns:local="clr-namespace:Schweinelatein"
        xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit" x:Class="Schweinelatein.MainWindow"
        mc:Ignorable="d"
        Title="Schweinelateinübersetzer" Height="415" Width="525" ResizeMode="CanMinimize" Closing="Window_Closing">
    <Grid>

        <RichTextBox x:Name="richTextBoxOrig" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Width="492" Height="150" ToolTip="Normaler Text"/>
        <RichTextBox x:Name="richTextBoxPig" HorizontalAlignment="Left" Margin="10,223,0,0" VerticalAlignment="Top" Width="492" Height="150" ToolTip="Schweinelatein"/>
        <Button x:Name="buttonTranslateNToPig"  HorizontalAlignment="Left" Margin="159,168,0,0" VerticalAlignment="Top" Width="343" Click="buttonTranslateNToPig_Click">
            <TextBlock x:Name="textblockNToPig" Text="Übersetzen"/>
        </Button>
        <TextBlock x:Name="textBlock" HorizontalAlignment="Left" Margin="10,174,0,0" TextWrapping="Wrap" VerticalAlignment="Top"><Run Text="Silbe"/></TextBlock>
        <TextBox x:Name="textBoxKey" TextWrapping="Wrap" Text="ay" Margin="41,170,363,184" TextAlignment="Center" Height="33"/>
        <Button x:Name="buttonTranslatePigToN" HorizontalAlignment="Left" Margin="159,196,0,0" VerticalAlignment="Top" Width="343" Click="buttonTranslatePigToN_Click">
            <TextBlock x:Name="textblockPigToN" Text="Übersetzen"/>
        </Button>
    </Grid>
</Window>