.Net 4.5 introduced a handy little new method Comparer<T>.Create to aid the creation of bespoke comparers, which is great because it means that you don’t have to define a new Comparer class when it is going to be needed once. In case you’re wondering, it’s still not possible to define anonymous implementation of interfaces in …
LINQ OrderBy – using Comparer<T>.Create and F#’s Object Expressions Read More »
Suppose you have an array of numbers, say, [1, 3, 5, 7, 9, …], and you want to pair each element up with its neighbour in the array, e.g. [[1, 3], [3, 5], [5, 7], [7, 9], …]. Sure, you can iterate through the indices of the elements and recursively grab the element at an …
.Net Tips – Use LINQ to create pairs of adjacent elements from a collection Read More »
Admit it, we’ve all done it before, writing those nasty nested loops just so we can iterate through multiple lists to get some combination/permutation of the lists, e.g.: 1: for (int i = 0; i < 10; i++) 2: { 3: for (int j = 0; j < 10; j++) 4: { 5: for (int …
I saw an interesting use of covariance today, consider an interface IMyClass and an implementing class MyClass: 1: public interface IMyClass { } 2: 3: public class MyClass : IMyClass { } If you want to convert an List<MyClass> to a List<IMyClass> you would normally use the Enumerable.Cast method but did you know that you …
Looking at these two images snapped right off MSDN, what do you notice? . . . that IEnumerable<T> extends IEnumerable but IList<T> doesn’t extend IList!? I know, peculiar isn’t it? Turns out, it was for a good reason: "A sequence of integers can be treated as a sequence of objects, by boxing every integer …
Found another interesting post on Eric Lippert’s blog, this one explain the rationales behind why there’s no built-in Enumerable.ForEach extension method, one which myself and no doubt many others had decided to implement ourselves. As he explains, there are two main philosophical reasons why he’s against such an extension method: "The first reason is that …
Eric Lippert on the decision to omit Enumerable.ForEach Read More »
As great as LINQ is and how it has transformed the way we interact with data in .Net to the point many of us wonder how we had managed without it all this time! There are however, some pitfalls one can fall into, especially with the concept of delayed execution which is easily the most …
This one took me by surprise a little but there’s something about the Enumerable.Except method which you ought to know about. At first you might have assumed (as I did) that given an array as the base set and calling the Except extension method with a second array will return all the items in the …
Yet another useful method on the Enumerable class, the SequenceEqual method does exactly what it says on the tin and tells you whether or not two sequences are of equal length and their corresponding elements are equal according to either the default or supplied equality comparer: As you know, for reference types the default equality …
Functional programming with Linq – Enumerable.SequenceEqual Read More »
Another gem I found on StackOverflow today (I’ve been spending a lot of time there these last couple of days..), this time in the form of a question on how to append or prepend a single value to an IEnumerable<T>. Greg provided an elegant solution to this particular problem, and here’s his answer: Which you …
Enumerable.Append and Enumerable.Prepend extension methods Read More »
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