File Equals. How can we determine if 2 files are equal? We can compare lengths, dates created and modified. But there is no way to know if the contents are the same unless we test them. We demonstrate a method that compares 2 files for equality.
Example. The simplest way to check 2 files for equal contents is to use File.ReadAllBytes on each file and then compare the result arrays. If the arrays have the same length, each byte must be compared for accurate results.
However: If the arrays have different lengths, we know the files are not equal.
File.ReadAllBytesNote: The output of this program will depend on the contents of the two files. Please change the paths in Main().
C# program that uses FileEquals
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);
}
}
Output
True
False
Usage. What sort of use does this method have? Let's say you are trying to update a directory of files but some files may not be different. Instead of rewriting files, you can test them for equality first.
So: If they are equal, you 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.