C# StreamReader

using (StreamReader sr = new StreamReader("test.txt"))
{
    string line = null;
    while (((line = sr.ReadLine())) != null)
    {
        Console.WriteLine(line);
    }
}

或者

using (StreamReader sr = new StreamReader("test.txt"))
{
    while (!sr.EndOfStream)
    {
        JPrint(sr.ReadLine());
    }
}