LINQ

LINQ OrderBy – using Comparer<T>.Create and F#’s Object Expressions

.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 Expres­sionsRead More »

.Net Tips – Use LINQ to create pairs of adjacent elements from a collection

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 col­lec­tionRead More »

Converting List<T> using covariance

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 …

Con­vert­ing List<T> using covari­anceRead More »

IList<T> doesn’t extend IList

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 …

IList<T> doesn’t extend IListRead More »

Eric Lippert on the decision to omit Enumerable.ForEach

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.ForEachRead More »

LINQ — Some pitfalls to look out for

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 …

LINQ — Some pit­falls to look out forRead More »

Enumerable.Except returns distinct items

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 …

Enumerable.Except returns dis­tinct itemsRead More »

Functional programming with Linq — Enumerable.SequenceEqual

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.SequenceEqualRead More »

Enumerable.Append and Enumerable.Prepend extension methods

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 meth­odsRead More »

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