/// <summary>
/// MD5
/// </summary>
/// <param name="file1"></param>
/// <param name="file2"></param>
/// <returns></returns>
private static bool CompareByMD5(string file1, string file2)
{
 // 使用.NET內(nèi)置的MD5庫(kù)
 using (var md5 = MD5.Create())
 {
 byte[] one, two;
 using (var fs1 = File.Open(file1, FileMode.Open))
 {
  // 以FileStream讀取文件內(nèi)容,計(jì)算HASH值
  one = md5.ComputeHash(fs1);
 }
 using (var fs2 = File.Open(file2, FileMode.Open))
 {
  // 以FileStream讀取文件內(nèi)容,計(jì)算HASH值
  two = md5.ComputeHash(fs2);
 }
 // 將MD5結(jié)果(字節(jié)數(shù)組)轉(zhuǎn)換成字符串進(jìn)行比較
 return BitConverter.ToString(one) == BitConverter.ToString(two);
 }
}

/// <summary>
/// https://stackoverflow.com/a/1359947
/// </summary>
/// <param name="file1"></param>
/// <param name="file2"></param>
/// <returns></returns>
private static bool CompareByToInt64(string file1, string file2)
{
 const int BYTES_TO_READ = sizeof(Int64); // 每次讀取8個(gè)字節(jié)
 int iterations = (int)Math.Ceiling((double)new FileInfo(file1).Length / BYTES_TO_READ); // 計(jì)算讀取次數(shù)

 using (FileStream fs1 = File.Open(file1, FileMode.Open))
 using (FileStream fs2 = File.Open(file2, FileMode.Open))
 {
 byte[] one = new byte[BYTES_TO_READ];
 byte[] two = new byte[BYTES_TO_READ];

 for (int i = 0; i < iterations; i++)
 {
  // 循環(huán)讀取到字節(jié)數(shù)組中
  fs1.Read(one, 0, BYTES_TO_READ);
  fs2.Read(two, 0, BYTES_TO_READ);

  // 轉(zhuǎn)換為Int64進(jìn)行數(shù)值比較
  if (BitConverter.ToInt64(one, 0) != BitConverter.ToInt64(two, 0))
  return false;
 }
 }

 return true;
}

/// <summary>
/// 讀入到字節(jié)數(shù)組中比較(轉(zhuǎn)為String比較)
/// </summary>
/// <param name="file1"></param>
/// <param name="file2"></param>
/// <returns></returns>
private static bool CompareByString(string file1, string file2)
{
 const int BYTES_TO_READ = 1024 * 10;

 using (FileStream fs1 = File.Open(file1, FileMode.Open))
 using (FileStream fs2 = File.Open(file2, FileMode.Open))
 {
 byte[] one = new byte[BYTES_TO_READ];
 byte[] two = new byte[BYTES_TO_READ];
 while (true)
 {
  int len1 = fs1.Read(one, 0, BYTES_TO_READ);
  int len2 = fs2.Read(two, 0, BYTES_TO_READ);
  if (BitConverter.ToString(one) != BitConverter.ToString(two)) return false;
  if (len1 == 0 || len2 == 0) break; // 兩個(gè)文件都讀取到了末尾,退出while循環(huán)
 }
 }

 return true;
}

/// <summary>
/// 讀入到字節(jié)數(shù)組中比較(使用LINQ的SequenceEqual比較)
/// </summary>
/// <param name="file1"></param>
/// <param name="file2"></param>
/// <returns></returns>
private static bool CompareBySequenceEqual(string file1, string file2)
{
 const int BYTES_TO_READ = 1024 * 10;

 using (FileStream fs1 = File.Open(file1, FileMode.Open))
 using (FileStream fs2 = File.Open(file2, FileMode.Open))
 {
 byte[] one = new byte[BYTES_TO_READ];
 byte[] two = new byte[BYTES_TO_READ];
 while (true)
 {
  int len1 = fs1.Read(one, 0, BYTES_TO_READ);
  int len2 = fs2.Read(two, 0, BYTES_TO_READ);
  if (!one.SequenceEqual(two)) return false;
  if (len1 == 0 || len2 == 0) break; // 兩個(gè)文件都讀取到了末尾,退出while循環(huán)
 }
 }

 return true;
}

/// <summary>
/// 讀入到字節(jié)數(shù)組中比較(while循環(huán)比較字節(jié)數(shù)組)
/// </summary>
/// <param name="file1"></param>
/// <param name="file2"></param>
/// <returns></returns>
private static bool CompareByByteArry(string file1, string file2)
{
 const int BYTES_TO_READ = 1024 * 10;

 using (FileStream fs1 = File.Open(file1, FileMode.Open))
 using (FileStream fs2 = File.Open(file2, FileMode.Open))
 {
 byte[] one = new byte[BYTES_TO_READ];
 byte[] two = new byte[BYTES_TO_READ];
 while (true)
 {
  int len1 = fs1.Read(one, 0, BYTES_TO_READ);
  int len2 = fs2.Read(two, 0, BYTES_TO_READ);
  int index = 0;
  while (index < len1 && index < len2)
  {
  if (one[index] != two[index]) return false;
  index++;
  }
  if (len1 == 0 || len2 == 0) break;
 }
 }

 return true;
}

/// <summary>
/// 讀入到字節(jié)數(shù)組中比較(ReadOnlySpan)
/// </summary>
/// <param name="file1"></param>
/// <param name="file2"></param>
/// <returns></returns>
private static bool CompareByReadOnlySpan(string file1, string file2)
{
 const int BYTES_TO_READ = 1024 * 10;

 using (FileStream fs1 = File.Open(file1, FileMode.Open))
 using (FileStream fs2 = File.Open(file2, FileMode.Open))
 {
 byte[] one = new byte[BYTES_TO_READ];
 byte[] two = new byte[BYTES_TO_READ];
 while (true)
 {
  int len1 = fs1.Read(one, 0, BYTES_TO_READ);
  int len2 = fs2.Read(two, 0, BYTES_TO_READ);
  // 字節(jié)數(shù)組可直接轉(zhuǎn)換為ReadOnlySpan
  if (!((ReadOnlySpan<byte>)one).SequenceEqual((ReadOnlySpan<byte>)two)) return false;
  if (len1 == 0 || len2 == 0) break; // 兩個(gè)文件都讀取到了末尾,退出while循環(huán)
 }
 }

 return true;
}

static void Main(string[] args)
{
 string file1 = @"C:\Users\WAKU\Desktop\file1.ISO";
 string file2 = @"C:\Users\WAKU\Desktop\file2.ISO";
 var methods = new Func<string, string, bool>[] { CompareByMD5, CompareByToInt64, CompareByByteArry, CompareByReadOnlySpan };
 foreach (var method in methods)
 {
 var sw = Stopwatch.StartNew();
 bool identical = method(file1, file2);
 Console.WriteLine("Method: {0}, Identical: {1}. Elapsed: {2}", method.Method.Name, identical, sw.Elapsed);
 }
}