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Taming Your Sequence’s Side-Effects Through IEnumerable.Let

Introduction Side-effects don’t fit together very well with functional-style delayed computation, as observed in LINQ. Having such constructs embedded in an otherwise eagerly evaluated imperative language like C# can cause quite some confusion from time to time. A few samples (due to Erik Meijer) of...

Posted to B# .NET Blog (Weblog) by bart on 09-12-2009
ExceLINQ – Not Your Typical LINQ Provider

Introduction On my last trip I had the opportunity to talk on the subject of LINQ once more. Geeky as we are, this time’s session title was “LINQ in breadth”, an orthogonal view on LINQ compared to my last year’s LINQ in depth talk. But what makes LINQ have a certain breadth? The simple answer: its spectrum...

Posted to B# .NET Blog (Weblog) by bart on 03-28-2009
Help! Drowning in Expression Trees, What Now?

Introduction Once more I found myself in LINQ providers land recently for a project yet unannounced. Given the relative poverty of the query language we’re targeting in that particular provider, a very common question came up: what about complex expressions in predicates? Let me give you an example:...

Posted to B# .NET Blog (Weblog) by bart on 02-12-2009
LINQ and The Matrix – Introducing MLinq

Today we’ll take a look at project “MLinq”, a very simple way to perform symbolic matrix calculations based on LINQ expression trees. Introduction But first, why would you even want to do this? Let me tell you I’m a big believer of the power of mathematical notation. Say you’ve been asked to write...

Posted to B# .NET Blog (Weblog) by bart on 02-10-2009
Dude, Where’s My LINQ DML?

Introduction On last week’s TechEd EMEA Developers 2008 conference in Spain I redelivered my talk on writing custom LINQ providers, showing off implementations of LINQ to AD and LINQ to SharePoint. One of the questions I received afterwards went along the lines of this blog post’s title: “Dude, where...

Posted to B# .NET Blog (Weblog) by bart on 11-22-2008
C# 4.0 Feature Focus - Part 3 - Intermezzo: LINQ's new Zip operator

After named parameters and optional parameters , we'll take a little breadth and deviate a bit from the language specifics to present a new LINQ operator: Zip. Just like a zipper zips two streams of materials together, LINQ's Zip operator can zip together two sequences. Here's the signature...

Posted to B# .NET Blog (Weblog) by bart on 11-03-2008
Who ever said LINQ predicates need to be Boolean-valued?

Note for purists: This post only speaks for “LINQ predicates”, not – although closely related to - the mathematic concept of a predicate as defined by Weisstein, Eric W. "Predicate." From MathWorld --A Wolfram Web Resource. http://mathworld.wolfram.com/Predicate.html as An operator in logic...

Posted to B# .NET Blog (Weblog) by bart on 09-14-2008
C# 3.0 Query Expression Translation Cheat Sheet

As a reference for some planned and unplanned future posts, I wanted to share out my “cheat sheet” for the C# 3.0 translation carried out for query expressions. Obviously it’s based on the C# 3.0 Language Specification more specially section 7.15.2. A few remarks that deserve more attention when reading...

Posted to B# .NET Blog (Weblog) by bart on 08-30-2008
What Do VB 9.0 Error “BC36593: Expression of type ‘X’ is not queryable.” And C# 3.0 Error “CS1936: Could not find an implementation of the query pattern for source type ‘X’.” Really Mean?

While preparing for another one of my posts, soon to be published, I received the following: What can one do when observing such a message? Since watching a grown man cry is both a pathetic and embarrassing situation, downloading the language specification is a good start. Here are my findings. Section...

Posted to B# .NET Blog (Weblog) by bart on 08-20-2008
The Most Funny Interface Of The Year … IQueryable<T>

Recently I delivered a talk at TechEd South Africa on “Custom LINQ Providers”. This is a very broad topic to cover in barely 60 minutes especially if one has to explain pretty “abstract” pieces of art like IQueryable<T>. Apparently I managed to do so looking at the scores <g>. But why is...

Posted to B# .NET Blog (Weblog) by bart on 08-15-2008

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