[UPDATE: Holy goodness. Apparently this was a more popular pasttime than I anticipated. There's like a hundred solutions in there. Who knew there were that many ways to stick commas in a string? It will take me some time to go through them all, so don...

I want to start by being absolutely positively clear about two things, because our usability research has shown this to be confusing. Remember our little program from last time? async void ArchiveDocuments(List<Url> urls) { Task archive = null;...

Here’s a crazy-seeming but honest-to-goodness real customer scenario that got reported to me recently. There are three DLLs involved, Alpha.DLL, Bravo.DLL and Charlie.DLL. The classes in each are: public class Alpha // In Alpha.DLL { public virtual void...

(This is part one of a two-part series on the loop-variable-closure problem. Part two is here .) UPDATE : We are taking the breaking change. In C# 5, the loop variable of a foreach will be logically inside the loop, and therefore closures will close over...

What happens here? class Animal { } class Mammal : Animal { } class Giraffe : Mammal { } class Reptile : Animal { } … static void Foo<T>(T t) where T : Reptile { } static void Foo(Animal animal) { } static void Main() { Foo(new Giraffe()); }...

Today I want your insights, opinions and advice. In any large organization over time people are going to move around within that organization, or leave it for various reasons, and therefore sometimes you need to bring in fresh new people to fill the...

Work has been crazy lately and I haven't had much time to work on SimpleScript. It's a lot of work starting from scratch! Right now I'm writing a templatized hash table for the binders and other lookup tables. I haven't written templatized C++ for a loooong...

JScript and VBScript have completely different garbage collectors. Occasionally people ask me how the garbage collectors work and what the differences are.

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[NOTE: Based on some insightful comments I have updated this article to describe more clearly the relationships between references, pointers and addresses. Thanks to those who commented.] I review a fair number of C# books; in all of them of course...

When we're designing a new version of the language, something we think about a lot is whether the proposed new features "hang together". Having a consistent "theme" to a release makes it easier for us to prioritize and organize proposals, it makes it...

No one I know at Microsoft asks those godawful "lateral-thinking puzzle" interview questions anymore. Maybe someone still does, I don't know. But rumour has it that a lot of companies are still following the Microsoft lead from the 1990s in their interviews...

A recent user question: I have code that maintains a queue of pending work items waiting to be completed on various different worker threads. In certain unfortunate fatal error situations I complete each of these by throwing an exception. Can I...

As I mentioned a while back, there are some bugs in the compiler code which analyzes whether a set of classes violates the “no cycles” rules for base classes. (That is, a class is not allowed to inherit from itself, directly or indirectly...

As you know if you've read this blog for a while , I'm disturbed by the myth that "value types go on the stack". Unfortunately, there are plenty of examples in our own documentation and in many books that reinforce this myth, either subtly or overtly...

As I discussed last time, were we to introduce interface and delegate variance in a hypothetical future version of C# we would need a syntax for it. Here are some possibilities that immediately come to mind. Option 1: interface IFoo<+T, -U>...

A Joel On Software reader asked the other day for examples of recursive functions other than old chestnuts like Fibonacci or factorial. Excellent question. I suggested topological sort , of course, but there are plenty of other examples that are way better...

I got a moral question from an author of programming language textbooks the other day requesting my opinions on whether or not beginner programmers should be taught how to use arrays. Rather than actually answer that question, I gave him a long list...

No tech today, but a little basic math. In baseball, a sport I know little about, apparently the Boston Red Sox have recently come back from a three game deficit to win a best-of-seven series against their traditional rival team, the New York Yankees...

Let’s start with something simple: an immutable stack. Now, immediately I hear the objection: a stack is by its very nature something that changes. A stack is an abstract data type with the interface void Push(T t); T Pop(); bool IsEmpty { get;...

The designers of C# 2.0 realized that writing iterator logic was painful. So they added iterator blocks. That way the compiler could figure out how to build a state machine that could store the continuation - the “what comes next” - in state somewhere...

"Ref returns" are the subject of another great question from StackOverflow that I thought I might share with a larger audience. Ever since C# 1.0 you've been able to create an "alias" to a variable by passing a "ref to a variable" to certain methods...

As you might have gathered from the number of times I make a blog post beginning with "I got the following question from a reader the other day..." I field a lot of questions about the C# language (and in the past fielded a lot of questions about VBScript...

I started programming on x86 machines during a period of large and rapid change in the memory management strategies enabled by the Intel processors. The pain of having to know the difference between “extended memory” and “expanded memory” has faded with...

Every now and then someone will ask me why the WSH shell object and the WSH network object are creatable from Visual Basic, but the actual root WScript object is not. I am always completely mystified by why people ask this! Why would you WANT to create the WScript object in a VB app?...

Suppose you have an immutable value type that is also disposable. Perhaps it represents some sort of handle. struct MyHandle : IDisposable { public MyHandle(int handle) : this() { this.Handle = handle; } public int Handle { get; private set; } public...