File.GetMD5 Method

public static string GetMD5(string targetFile)
 {
     using (var md5 = System.Security.Cryptography.MD5.Create())
     {
         using (var Stream = System.IO.File.OpenRead(targetFile))
         {
             var hashBytes = md5.ComputeHash(Stream);
             var sb = new StringBuilder();
             foreach (var t in hashBytes)
                 sb.Append(t.ToString("X2"));
             return Convert.ToString(sb);
         }
     }
 }