Note The output of this program will depend on the contents of the two files. Please change the paths in Main().
using System;
using System.IO;
class Program
{
static bool FileEquals(string path1, string path2)
{
byte[] file1 = File.ReadAllBytes(path1);
byte[] file2 = File.ReadAllBytes(path2);
if (file1.Length == file2.Length)
{
for (int i = 0; i < file1.Length; i++)
{
if (file1[i] != file2[i])
{
return false;
}
}
return true;
}
return false;
}
static void Main()
{
bool a = FileEquals("C:\\stage\\htmlmeta",
"C:\\stage\\htmlmeta-aspnet");
bool b = FileEquals("C:\\stage\\htmllink",
"C:\\stage\\htmlmeta-aspnet");
Console.WriteLine(a);
Console.WriteLine(b);
}
}True
False
FileInfo note. If the common case in your program is that the files are not equal, then using a FileInfo struct and the Length property to compare lengths first would be faster.
Usage. Suppose we are trying to update a directory of files but some files may not be different. Instead of rewriting files, we can test them for equality first.
So If they are equal, we can just do nothing. Reading in a file is a lot faster than writing out a file.
Therefore In this use case, this FileEquals method can significantly improve performance.
A summary. We can guess whether two files are equal by testing their dates and lengths. But we cannot know if every single byte is equal unless we test every single byte.