public void ChooseDocument(string fileName)
{
string format = fileName.Substring(fileName.Length - 4);
switch (format.ToLower())
{
case ".txt": handler = new TXTHandler(fileName);
break;
case ".doc": handler = new DOCHandler(fileName);
break;
case ".xml": handler = new XMLHandler(fileName);
break;
default: Console.WriteLine("Неопознаный формат");
break;
}
}