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

public static class Signature
{
    public static string CalculateHash(string path)
    {
        string hash;
        using (var hasher = MD5.Create())
        using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, 4096, true))
        {
            var hashBytes = hasher.ComputeHash(stream);
            var hashBuilder = new StringBuilder();
            foreach (byte b in hashBytes)
                hashBuilder.Append(b.ToString("x2").ToLower());
            hash = hashBuilder.ToString();
        }
        return hash;
    }
}