class IO

void IO.Foreach(string path, Encoding encoding, Action<string> block)

string[] IO.Foreach(string path, Encoding encoding)

Example

IO.Foreach("lines.txt", Encoding.UTF8, line =>
    Console.WriteLine(line));

If write same logick in C# basic expression.

using (var reader = new StreamReader("lines.txt", Encoding.UTF8))
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}

void IO.Foreach(string path, Action<string> block)

void IO.Foreach(string path)

Use default encoding Encoding.Default.