C#检测两个文件内容是否相同

不知道为什么对Excel 2010 xlsx后缀的文件没有效果，求解！

对其他文件有效，如.txt,.csv

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

namespace CheckFile
{
    class Program
    {
        static void Main(string[] args)
        {
            string filePath1 = @"D:/1.txt";
            string filePath2 = @"D:/2.txt";
            bool result = CheckFile(filePath1, filePath2);
            Console.WriteLine(result.ToString());
            Console.ReadKey();

        }
        /// <summary>
        /// Check File
        /// </summary>
        /// <param name="filePath1"></param>
        /// <param name="filePath2"></param>
        /// <returns></returns>
        public static bool CheckFile(string filePath1, string filePath2)
        {
            using (HashAlgorithm hash = HashAlgorithm.Create())
            {
                using (FileStream file1 = new FileStream(filePath1, FileMode.Open, FileAccess.Read)
                    , file2 = new FileStream(filePath2, FileMode.Open, FileAccess.Read))
                {
                    byte[] hashByte1 = hash.ComputeHash(file1);
                    byte[] hashByte2 = hash.ComputeHash(file2);
                    string str1 = BitConverter.ToString(hashByte1);
                    string str2 = BitConverter.ToString(hashByte2);
                    return (str1 == str2);
                }
            }
        }
    }
}