public class NameCounterList : List<string>
{
    private Dictionary<string, int> _names = 
        new Dictionary<string, int>();

    public new void Add(string item)
    {
        base.Add(item);

        if (_names.ContainsKey(item.ToLower()))
            _names[item.ToLower()]++;
        else
            _names.Add(item.ToLower(), 1);
    }

    public new void Clear()
    {
        base.Clear();
        _names.Clear();
    }

    public override string ToString()
    {
        StringBuilder sb = new StringBuilder();
        if (this._names.Count > 0)
        {
            Dictionary<string, int>.Enumerator en = 
                this._names.GetEnumerator();
            while (en.MoveNext())
            {
                sb.Append(en.Current.Key);
                sb.Append(": ");
                sb.Append(en.Current.Value.ToString());
                sb.Append(System.Environment.NewLine);
            }
        }
        return sb.ToString();
    }
}

NameCounterList ncl = new NameCounterList();
ncl.Add("Peter");
ncl.Add("Harry");
ncl.Add("Sabine");
ncl.Add("Sabine");
ncl.Add("Jörg");
ncl.Add("Harry");
ncl.Add("Harry");
Console.WriteLine(ncl.ToString());

peter: 1
harry: 3
sabine: 2
jörg: 1

private List GetDbFactoryClasses()
{
    List factClasses = new List();
    DataTable dt = DbProviderFactories.GetFactoryClasses();
    if (dt != null)
    {
        foreach (DataRow dr in dt.Rows)
        {
            factClasses.Add(dr[2].ToString());
        }
    }
    return factClasses;
}

// Nur der Vollständigkeit halber
// Wird normalerweise aus einer Konfiguration gelesen
 
string strProviderInvariantName = "System.Data.SqlClient";
string strConnectionString = "...";


// Laden des Providers
// Erstellen der Datenbank-Verbindung
// Zuweisung des notwendigen ConnectionStrings
 
DbProviderFactory dbFactory = 
    DbProviderFactories.GetFactory(strProviderInvariantName);
DbConnection dbConnection = dbFactory.CreateConnection();
dbConnection.ConnectionString = strConnectionString;

XmlDocument doc = new XmlDocument();
doc.Load("categories.xml");
XmlNode xnRoot = doc.SelectSingleNode("/categories");

XmlTextReader xtr = 
    new XmlTextReader(new StringReader(category.ToXml()));

XmlNode xnCategory = doc.ReadNode(xtr);
xnRoot.AppendChild(xnCategory);