C#’s linq(language-integrated query) features are some of the more powerful features available through the language. Aside from it’s query operators that are, as it’s name would suggest, integrated into the language, the feature also brings along a large set of Extension methods to the IEnumerable
One interesting re-use of the IEnumerable
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class Program { static void Main(string[] args) { Random rgen = new Random(); var doubles = (from p in Enumerable.Range(0, 100) select rgen.NextDouble()); doubles.EachCase( (t) => t < 0.5d, (value) => { Console.WriteLine(value.ToString() + " is less than 0.5d."); }).EachCase( (t) => t > 0.75d, (value) => { Console.WriteLine(value.ToString() + " is greater than 0.75d."); }).EachCase((t) => true, (value) => { Console.WriteLine(value.ToString() + " is not handled..."); }).Count(); Console.ReadKey(); } } |
What we have here is similar- but not quite the same- as a switch statement within a loop. What makes this particularly interesting as a structure is that it acts sort of like a seive. The source to the extension EachCase() method is shown here:
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public static class SelectExtension { public static IEnumerable<T> EachCase<T>(this IEnumerable<T> Enumeration,Func<T,bool> TestExpression,Action<T> CodeBlock) { if (Enumeration == null) yield break; foreach (var iterate in Enumeration) { if (TestExpression(iterate)) { CodeBlock(iterate); } else yield return iterate; } } } |
The function works by calling the passed Action for all entries in the enumeration that cause TestExpression to return true. Those that return false are yielded to the caller. In the original code the EachCase() calls were chained, one after the other; each one operated on the entries that the previous one didn’t work with. the final .Count() call in the original code is to force it to be enumerated, allowing all the code blocks to evaluate appropriately. What use-cases might this have? I have no idea. However I feel confident in saying that it could make for a more readable alternative to something that might otherwise require a separate Finite-State machine.
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