using System.Text.RegularExpressions;
...
private bool IsStringValidGuid(string s)
{
    return string.IsNullOrEmpty(s) ? false : new Regex(@"^(\{{0,1}([0-9a-fA-F]){8}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){12}\}{0,1})$").IsMatch(s);
}

using System.Text.RegularExpressions;
...
public static bool IsStringValidGuid(this string s)
{
    return string.IsNullOrEmpty(s) ? false : new Regex(@"^(\{{0,1}([0-9a-fA-F]){8}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){12}\}{0,1})$").IsMatch(s);
}

/// <summary>
/// Prueft ob der uebergebene String eine Guid ist.
/// </summary>
/// <param name="s">string</param>
/// <returns>bool</returns>
public bool IsStringValidGuid(string s)
{
    int hexchars = 0;
    foreach (char c in s)
    {
        if (IsValidHexChar(c))
            hexchars++;
    }
    return hexchars == 32;
}
private bool IsValidHexChar(char hexChar)
{
    return (hexChar >= 0x30 && hexChar <= 0x39) //IsValidHexDigit
        || (hexChar >= 0x61 && hexChar <= 0x66) //IsValidLowerHexLetter
        || (hexChar >= 0x41 && hexChar <= 0x46); //IsValidUpperHexLetter
}

/// <summary>
/// Prueft ob der uebergebene String eine Guid ist.
/// </summary>
/// <param name="s">string</param>
/// <returns>bool</returns>
public static bool IsStringValidGuid(this string s)
{
    int hexchars = 0;
    foreach (char c in s)
    {
        if (IsValidHexChar(c))
            hexchars++;
    }
    return hexchars == 32;
}
private bool IsValidHexChar(char hexChar)
{
    return (hexChar >= 0x30 && hexChar <= 0x39) //IsValidHexDigit
        || (hexChar >= 0x61 && hexChar <= 0x66) //IsValidLowerHexLetter
        || (hexChar >= 0x41 && hexChar <= 0x46); //IsValidUpperHexLetter
}

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
    if (value.ToString() == String.Empty)
        return null;
 
    decimal val = decimal.Parse(value.ToString());
 
    return (val < 0) ? Brushes.Red : Brushes.Green;
}
 
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
    return value;
}
}

<Window.Resources>
    <Converters:SignedUnsignedConverter x:Key="SignedUnsigned" />
</Window.Resources>

<DataGrid Name="dataGrid" AutoGenerateColumns="False" MouseDoubleClick="dataGrid_MouseDoubleClick">
    <DataGrid.Columns>
        <DataGridTextColumn Header="Name" Binding="{Binding Name}" />
        <DataGridTemplateColumn Header="Price">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Price}" Background="{Binding Price, Converter={StaticResource SignedUnsigned}}" />
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

<TextBox Name="textBox" Background="{Binding ElementName=textBox, Path=Text, Converter={StaticResource SignedUnsigned}}"/>

<configuration>
  <appSettings>
    <add key="DATASOURCE" value="../../DataBase/data" />
  </appSettings>
</configuration>

private string DataSource = ConfigurationManager.AppSettings.Get("DATASOURCE");

SQLiteConnection connection;
 
private void OpenConnection()
{
    connection = new SQLiteConnection();
    connection.ConnectionString = "Data Source=" + DataSource;
    connection.Open();
}

private void CloseConnection()
{
    connection.Close();
    connection.Dispose();
}

OpenConnection();
 
using (var command = new SQLiteCommand(connection))
{
    command.CommandText = string.Format("INSERT INTO Entities (Beschreibung, HtmlName, Unicode, Zeichen) VALUES('{0}', '{1}', '{2}', '{3}')",
                    entity.Beschreibung, entity.HtmlName, entity.Unicode, entity.Zeichen);
 
    command.ExecuteNonQuery();
}
 
CloseConnection();

OpenConnection();
 
List<HtmlEntity> entities = new List<HtmlEntity>();
using (var command = new SQLiteCommand(connection))
{
    command.CommandText = "SELECT * FROM Entities";
 
    using (SQLiteDataReader reader = command.ExecuteReader())
    {
        while (reader.Read())
        {
            entities.Add(new HtmlEntity
            {
                Beschreibung = reader[0].ToString(),
                HtmlName = reader[1].ToString(),
                Unicode = reader[2].ToString(),
                Zeichen = reader[3].ToString()
 
            });
        }
        reader.Close();
    }
}
 
CloseConnection();

OpenConnection();
 
using (var command = new SQLiteCommand(connection))
{
    command.CommandText = string.Format("DELETE FROM Entities WHERE Beschreibung = '{0}' AND HtmlName = '{1}' AND Unicode = '{2}' AND Zeichen =  '{3}'",
        entity.Beschreibung, entity.HtmlName, entity.Unicode, entity.Zeichen);
 
    command.ExecuteNonQuery();
}
 
CloseConnection();

<startup useLegacyV2RuntimeActivationPolicy="true">
	<supportedRuntime version="v4.0"/>
</startup>

public void  InsertData(HtmlEntity entity)
{
    using (var context = new HtmlEntityEntities())
    {
        context.AddToEntities(entity);
        context.SaveChanges();
    }
}

public List<HtmlEntity> GetAllHtmlEntities()
{
    List<HtmlEntity> entities;
 
    using (var context = new HtmlEntityEntities())
    {
        entities = (from e in context.Entities
                    select e).ToList();
 
    }         
 
    return entities;
}

public void DeleteData(HtmlEntity entity)
{
    using (var context = new HtmlEntityEntities())
    {
        HtmlEntity obj = (HtmlEntity)context.GetObjectByKey(entity.EntityKey);
 
 
        context.DeleteObject(obj);
        context.SaveChanges();
    }
}

using (var context = new HtmlEntityEntities())
{  
    return (from e in context.Entities                        
            where e.Beschreibung == keyword                      
            select e).FirstOrDefault();
}

public static class ExtensionMethods
{
    public static bool IsPalindrome(this string value)
    {
        //von Leer- und Sonderzeichen befreien
        value = value.ToLower().RemoveSpecialCharacters();
 
        int minValue = 0;
        int maxValue = value.Length - 1;
 
        var charArray = value.ToCharArray();
 
        for (int i = 0; i < value.Length - 1; i++)
        {
            if (charArray[minValue] == charArray[maxValue])
            {
                minValue++;
                maxValue--;
                continue;
            }
            else
                return false;
        }
        return true;
    }
 
    public static string RemoveSpecialCharacters(this string value)
    {
        return Regex.Replace(value, @"[^a-zA-Z0-9]", string.Empty);
    }
}

class Program
{
    static void Main(string[] args)
    {
        PalindromFactory factory = new PalindromFactory();
        var palindrome = factory.GetPalindrome();
        string output = "{0} ist {1}ein Palindrom";
 
        foreach (var palindrom in palindrome)
        {
            Console.WriteLine(String.Format(output, palindrom, palindrom.IsPalindrome() ? "" : "k"));
        }
 
        var palindromSaetze = factory.GetPalindromSaetze();
        foreach (var palindrom in palindromSaetze)
        {
            Console.WriteLine(String.Format(output, palindrom, palindrom.IsPalindrome() ? "" : "k"));
        }
    }
}

/// Stellt eine Sammlung von Palindrome und Palindromsätze bereit
/// Quelle Wikipedia
/// http://de.wikipedia.org/wiki/Liste_deutscher_Palindrome
public class PalindromFactory
{
    private List<string> Palindrome { get; set; }
 
    public List<string> GetPalindrome()
    {
        Palindrome = new List<string>
        {
            "Aha",
            "Amokoma",
            "Amoralaroma",
            "Anina",
            "Anna",
            "Annasusanna",
            "Aua",
            "Bob",
            "Bub",
            "Burggrub",
            "Biggle", //kein Palindrom
            "Mario", //kein Palindrom
            "Mongognom",
            "Nebelleben",
            "neben",
            "Neffen",
            "nennen",
            "netten",
            "netzten",
            "Neozoen",
            "nun",
            "Omo",
            "Otto",
            "Priebe" //kein Palindrom
            };
 
        return Palindrome;
    }
 
    public List<string> GetPalindromSaetze()
    {
        Palindrome = new List<string>
        {
            "Die Liebe fleht: Helfe bei Leid!",
            "Die Liebe geht, hege Beileid!",
            "Die Liebe, ist sie Beileid?",
            "Die Liebe ist Sieger, rege ist sie bei Leid.",
            "Die Liebe ist Sieger, stets rege ist sie bei Leid.",
            "Die Niere bot Komik: nass sank im Oktober ein Eid.",
            "Die Rede — ist sie der Eid?",
            "Dreh Magiezettel um, Amulette zeig am Herd!",
            "Du, erfror Freud?",
            "Der Fred",
            "Eine güldne, gute Tugend: Lüge nie!",
            "Eine Horde bedrohe nie!",
            "Eine Hure ruhe nie.",
            "Eine Note betone nie.",
            "Eine so Kesse kose nie.",
            "Eine treue Familie bei Lima feuerte nie.",
            "Einhorn roh? Nie!",
            "Eins nutzt uns: Amore. Die Rederei da, die Rederei der Omas nutzt uns nie.",
            "Eis feil! Ei, wo Eis feil lief sie, o wie lief sie.",
            "Elietta hat Teile.",
            "Ella rüffelte Detlef für alle.",
            "Elly biss Sibylle.",
            "Emma, behend 'ne Hebamme!",
            "Emma, so litt Tilos Amme!",
            "Emmas Amme",
            "Er habe nie eine Bahre.",
            "Erhabene Bahre",
            "Erhöre nie eine Röhre.",
            "Erika feuert nur untreue Fakire.",
            "Erol, red nie in der Lore.",
            "Alles hat seine Zeit, nur die alten Weiber nicht.", //Kein Palindromsatz
            "Es eilt, immer ahnend Nebel, reger der Flegel Fred, reg' erlebend nen Harem mit Liese.",
        };
 
        return Palindrome;
 
    }
}