Question

I want to replace a binary file if the contents are different.

So I need to be able to compare the binary file (without having to deserialize it).

Is this possible?

I used binary formatter to save the file.

Answer 1

Yes, you can generate the MD5 or SHA1 hash for each set of file data and then compare them.

Sample code (error checking removed for clarity):

public bool CompareFiles(string filePath1, string filePath2)
{

  FileInfo info1 = new FileInfo(filePath1);
  FileInfo info2 = new FileInfo(filePath2);


  byte[] data1 = new byte[info1.Length]
  byte[] data2 = new byte[info2.Length]; 

  FileStream fs1 = new FileStream(filePath1, FileMode.Open);
  FileStream fs2 = new FileStream(filePath2, FileMode.Open);

  fs1.Read(data1, 0, info1.Length);
  fs2.Read(data2, 0, info2.Length);

  fs1.Dispose();
  fs2.Dispose();

  SHA1 sha = new SHA1CryptoServiceProvider(); 

  byte[] hash1 = sha.ComputeHash(data1);
  byte[] hash2 = sha.ComputeHash(data2);

  // c# 2 or less: you need to compare the hash bytes yourself

  // c# 3.5/4
  bool result = hash1.SequenceEqual(hash2);

  return result;
}