12.14. Calculate the Hash Code of a File
Problem
You need to determine if the contents of a file have changed over time.
Solution
Create a cryptographic hash code of the file's contents using the ComputeHash method of the System.Security.Cryptography.HashAlgorithm class. Store the hash code for future comparison against newly generated hash codes.
How It Works
As well as allowing you to store passwords securely (discussed in recipe 12-13), hash codes provide an excellent means of determining if a file has changed. By calculating and storing the cryptographic hash of a file, you can later recalculate the hash of the file to determine if the file has changed in the interim. A hashing algorithm will produce a very different hash code even if the ...
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