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private ArrayList ReadFile(string path)
        {
            ArrayList dataList = new ArrayList();
            if (File.Exists(path))
            {
                StreamReader sr = new StreamReader(path);
                string data = sr.ReadToEnd(); sr.Close(); if
                    (!string.IsNullOrEmpty(data))
                {
                    dataList.AddRange(data.Split(new string[] { "\r\n" }, StringSplitOptions.RemoveEmptyEntries));
                }
            }
            return dataList;
        }

// ...

arr = (string[]) ReadFile("datei.txt").ToArray(typeof(string));					

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private List<string> ReadFile(string path)
        {
            List<string> dataList = new List<string>();
            if (!File.Exists(path)) return null;
            string data = File.ReadAllLines(path);
            foreach(string s in data.Split('\n', '\r')) dataList.Add(s);                 
            return dataList;
        }

// ...

//Entweder
List<string> arr = ReadFile("datei.txt");
//Oder
string[] arr = ReadFile("datei.txt").ToArray();