void Main()
{
    var matches = Regex.Matches(File.ReadAllText(@"C:\Users\Vasaka\Desktop\example_ndisprot.txt"),
                @"(?<name>\w+):\sEnd,?\s(?<val>\d{6})");
    (from Match match in matches
    group match.Groups["val"].Value by match.Groups["name"].Value)
    .ToList()
    .ForEach(grp => File.AppendAllText(grp.Key+".txt",string.Join("\n",grp.Select(x=>x))));
}