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Time and culture

The problem

Yesterday we find a cool bug in code. The code is really simple and was working on 3 of 4 machines. The problematic code is following:

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var path = @" E:\tmp\test_" + DateTime.Today.ToShortDateString()+".tmp";

using (var file = new FileStream(path, FileMode.Create, FileAccess.Write))
{
    //something
}

The exception was System.IO.DirectoryNotFoundException in FileStream and we of course checked that E:\tmp\ exists. Moreover the error was only one one machine

The solution

You can run above code on your machine and I am almost sure that if it works correctly. But If you add following line

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CultureInfo.DefaultThreadCurrentCulture = new CultureInfo("en-us");

it will throw an error. Why? Because directory: E:\tmp\test_2\13\ does not exist. In polish culture the file E:\tmp\2015-02-13.tmp is created without problems, because it does not contains any \

Thing to remember

Be careful we culture specific date formating, especially when we use them in paths.

The funny thing is that any unit test did not find that issue.

This post is licensed under CC BY 4.0 by the author.