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 »
For a while now I’ve been wondering why C#’s support for covariance does not cover value types, both in normal array covariance and covariance in the generic parameter introduced in C# 4: 1: void Main() 2: { 3: int i = 0; 4: string str = "hello world"; 5: 6: TestMethod(i); // legal 7: TestMethod(str); …
The other day I had an interesting observation on the optional parameters in C# 4, whereby if you specify a parameter as optional on an interface you don’t actually have to make that parameter optional on any implementing class: 1: public interface MyInterface 2: { 3: void TestMethod(bool flag=false); 4: } 5: 6: public class …
Interesting observation on C# 4’s optional parameter 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 …
If you’ve been using S3 client in the AWS SDK for .Net you might have noticed that there are no methods that let you interact with the folders in a bucket. As it turns out, S3 does not support folders in the conventional sense*, everything is still a key value pair, but tools such as …
Java vs C# As Jon Skeet pointed out in this excellent article on closures, the strategies of capturing the execution context which the behaviour is bound to different between Java and C#. C# captures the variable itself, whereas Java captures the value of the variable. To illustrate the difference, here’s Jon’s original example in C#: …
In my last post I explained the difference between the techniques of Currying and Partial Application, following on where there let me show you how you might apply these two techniques in F#, Javascript and C#. F# Starting with F#, being a functional language it makes currying and partial application dead easy (considering that they …
Currying and Partial Applications in F#, Javascript and C# Read More »
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 …
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