I don't understand the point you're trying to make with your example. Is the con...

jcparkyn · on March 4, 2023

FileInfo is a stateful reference type, so overriding Equals and GetHashCode to use value equality would be a Bad Idea™.

E.g.:

    var f = new FileInfo("image.jpg");
    var set = new HashSet<FileInfo> { f };
    f.MoveTo("image2.jpg");
    Console.WriteLine(set.Contains(f)); // Would be false (sometimes)

nine_k · on March 5, 2023

Then FileInfo should not be hashable, so a Set of it could not even be declared.

jcparkyn · on March 6, 2023

But the current implementation using reference equality is perfectly valid, and often quite useful.

thangalin · on March 6, 2023

https://en.wikipedia.org/wiki/Principle_of_least_astonishmen...

Here's another:

    string path = "/tmp/filename.txt";
    FileInfo f = new FileInfo( path );

    File.CreateText( path ).Dispose();
    Assert.True( f.Exists );

    f.Delete();
    Assert.False( f.Exists );

Astonishingly, the test fails because the result of Exists is cached. ¯\_(ツ)_/¯

My expectation is that if I put two things that are identical---for all intents and purposes---into a set, only one copy is added to the set. Likewise, upon deleting a file, I expect that testing for its existence always returns false. Both of these expectations are based on my mental models for math and file systems.

I haven't tested the behaviour of caching file states in Java, but I suspect it will return false if the file is deleted. Point being, in my limited time with C#, I've found it to violate the principle of least astonishment in ways that Java does not.