LINQ

Table of Contents You may consider it a little odd to have a list of posts as the final part in the series, but it makes sense when you consider that visiting the Edulinq tag page shows results in reverse chronological order. At that point, a newcomer will hopefully hit this post first, and then find it easier to navigate to the first post. Anyway… Introduction Where Select Range Empty Repeat Count and LongCount Concat SelectMany Any and All First, Single, Last and the …OrDefault versions DefaultIfEmpty Aggregate Distinct Union Intersect Except ToLookup Join ToList GroupBy GroupJoin Take, Skip, TakeWhile, … Continue reading Reimplementing LINQ to Objects: Part 45 – Conclusion and List of Posts

I promised a post on some questions of design that are raised by LINQ to Objects. I suspect that most of these have already been covered in other posts, but it may well be helpful to talk about them here too. This time I’ve thought about it particularly from the point of view of how other APIs can be built on some of the same design principles, and the awkward choices that LINQ has thrown up. The power of composability and immutability Perhaps the most important aspect of LINQ which I’d love other API designers to take on board is … Continue reading Reimplementing LINQ to Objects: Part 44 – Aspects of Design

I’ve been putting off writing about this for a while now, mostly because it’s such a huge topic. I’m not going to try to give more than a brief introduction to it here – don’t expect to be able to whip up your own LINQ to SQL implementation afterwards – but it’s worth at least having an idea of what happens when you use something like LINQ to SQL, NHibernate or the Entity Framework. Just as LINQ to Objects is primarily interested in IEnumerable<T> and the static Enumerable class, so out-of-process LINQ is primarily interested in IQueryable<T> and the static … Continue reading Reimplementing LINQ to Objects: Part 43 – Out-of-process queries with IQueryable

A few parts ago, I jotted down a few thoughts on optimization. Three more topics on that general theme have occurred to me, one of them prompted by the comments. User-directed optimizations I mentioned last time that for micro-optimization purposes, we could derive a tiny benefit if there were operators which allowed us to turn off potential optimizations – effectively declare in the LINQ query that we believed the input sequence would never be an IList<T> or an ICollection<T>, so it wasn’t worth checking it. I still believe that level of optimization would be futile. However, going the other way … Continue reading Reimplementing LINQ to Objects: Part 42 – More optimization

Okay, first a quick plug. This won’t be in as much detail as chapter 11 of C# in Depth. If you want more, buy a copy. (Until Feb 1st, there’s 43% off it if you buy it from Manning with coupon code j2543.) Admittedly that chapter has to also explain all the basic operators rather than just query expression translations, but that’s a fair chunk of it. If you’re already familiar with query expressions, don’t expect to discover anything particularly insightful here. However, you might be interested in the cheat sheet at the end, in case you forget some of … Continue reading Reimplementing LINQ to Objects: Part 41 – How query expressions work

I’m not an expert in optimization, and most importantly I don’t have any real-world benchmarks to support this post, so please take it with a pinch of salt. That said, let’s dive into what optimizations are available in LINQ to Objects. What do we mean by optimization? Just as we think of refactoring as changing the internal structure of code without changing its externally visible behaviour, optimization is the art/craft/science/voodoo of changing the performance of code without changing its externally visible behaviour. Sort of. This requires two definitions: "performance" and "externally visible behaviour". Neither are as simple as they sound. … Continue reading Reimplementing LINQ to Objects: Part 40 – Optimization

While implementing Edulinq, I only focused on two implementations: .NET 4.0 and Edulinq. However, I was aware that there were other implementations available, notably LinqBridge and the one which comes with Mono. Obviously it’s interesting to see how other implementations behave, so I’ve now made a few changes in order to make the test code run in these different environments. The test environments I’m using Mono 2.8 (I can’t remember the minor version number offhand) but I tend to think of it as "Mono 3.5" or "Mono 4.0" depending on which runtime I’m using and which base libraries I’m compiling … Continue reading Reimplementing LINQ to Objects: Part 39 – Comparing implementations

I mentioned before that the Zip operator was only introduced in .NET 4, so clearly there’s a little wiggle room for LINQ to Object’s query operators to grow in number. This post mentions some of the ones I think are most sorely lack – either because I’ve wanted them myself, or because I’ve seen folks on Stack Overflow want them for entirely reasonable use cases. There is an issue with respect to other LINQ providers, of course: as soon as some useful operators are available for LINQ to Objects, there will be people who want to apply them to LINQ … Continue reading Reimplementing LINQ to Objects: Part 38 – What’s missing?