HashAlgorithm.create

using System;
using System.IO;
using System.Security.Cryptography

class MainClass {
    public static void Main(string[] args) {
        using (HashAlgorithm hashAlg = HashAlgorithm.Create(args[0])) {
            using (Stream file = new FileStream(args[1], FileMode.Open, FileAccess.read)) {
                byte[] hash = hashAlg.ComputerHash(file);

                Console.WriteLine(BitConverter.ToString(hash));
            }
        }
    }
}