An effective strategy for handling exceptions is to catch them at the boundary of a coarsely-grained "unit of work". Once you've caught an exception, you need to repair application state, notify affected people and ultimately abort the program, retry the operation, or ignore the error. This article provides guidelines for making that decision.

A paper by Thibaud Lopez Schneider shows that we can transform a function written with conventional control structures and synchronous function calls into a set of callback functions that work in an asychronous environment, such as an RIA that uses XHR. Longer-term, tools may evolved that will automate this process, to simplify the development of correct asynchronous applications.

Too many programmers catch exceptions too often, causing both mainline and error handling logic to be complex and error-prone. Although C#, PHP and other languages don't make the mistake that Java made with Checked Exceptions, Java trained a generation of programmers in bad habits. A strategy that (i) uses finally as the first resort for containing corrupting and maintaining invariants, (ii) uses catch locally when the exceptions thrown in an area are completely understood, and (iii) surrounds independent units of work with try-catch blocks is an effective basis for using exceptions that can be built upon to develop an exception handling policy for a particular application.

The Multiton design pattern is an extension of the Singleton pattern that can be useful for managing state updates in GUI applications, in particular, asynchronous RIA's. This article introduces the multiton pattern and demonstrates a practical use, while revealing that the Multiton pattern interacts poorly with garbage collectors and doesn't apply well when a large number of objects are created.

When people start developing RIA’s in environments such as Silverlight, GWT, Flex and plain JavaScript, they often write asynchronous communication callbacks in an unstructured manner, putting them wherever is convenient — often in an instance member of a user interface component (Silverlight and GWT) or in a closure or global function (JavaScript.) Several problems almost invariably occur as applications become more complex that force the development of an architecture that decouples communication event handlers from the user interface: a straightforward solution is to create a model layer that’s responsible for notifying interested user interface components about data updates.

Today's popular programming languages support some form of Dictionary that maps a set of keys to values. On close inspection, we find that common languages offer programmers different options for dealing with missing values. This article looks at the handling of missing keys in four popular languages and presents a PHP function and C# extension method that implement a particularly useful get() operator.

Bessen and Meurer's data suggest that outside of the chemical and pharmaceutical industries, litigation costs for the average public firm actually exceed profits from their patent portfolio by a wide margin. By 1999, the last year in their sample, defendending against patent lawsuits cost non-chemical public firms about $12 billion, while their patent portfolios generated only about $3 billion in profits. This data suggests that outside the chemical and pharmaceutical industries, the patent system actually reduces the net returns to innovation; firms don't earn enough from their patents to offset the costs of defending themselves against patent infringement lawsuits brought by other firms.

Extension methods are the most controversial feature that Microsoft has introduced in C# 3.0. Introduced to support the LINQ query framework, extension methods make it possible to define new methods for existing classes. Although extension methods can greatly simplify code that uses them, many are concerned that they could transform C# into something that programmers find unrecognizable, or that C#’s namespace mechanisms are inadequate for managing large systems that use extension methods. Adoption of the LINQ framework, however, means that extension methods are here to stay, and that .net programmers need to understand how to use them effectively, and, in particular, how extension methods are different from regular methods.

Microsoft SQL Server requires you to know the name of a constraint when you drop it. This isn't a problem when using the GUI, but it makes it difficult to write migration scripts. This article presents a simple stored procedure which uses information in the system data dictionary to allow deletion of constraints knowing only the table and column name.

C# offers two casting operators: the prefix-cast and the as-cast. Although the two operators compile to different op-codes in the CLR, the practical difference between them is in how they handle failed casts. Prefix-cast throws an exception on cast failure, while as-cast returns null. It’s easier to implement correct error handling when you use prefix cast, because it doesn’t require manual checks for null values that can cause problems in distant parts of your program. Prefix-cast should be the default cast operator on your fingertips, that you use for everyday situations

It can be tricky writing database migrations for SQL Server since you often need to refer to constraints and keys by name. This article presents a simple stored procedure that queries the system catalog to find the primary key constraint of a table and remove it in one step.

Nice article about Dynamic SQL for Microsoft's SQL Server. How to do it, why you should do it, and why you shouldn't.

Languages that support multiline quotes such as C#, Perl and PHP make it easy for developers to embed SQL code in applications in a readable and maintainable way

When Rich Internet Applications reach a certain level of complexity, you start having concurrency problems similar, but not identical, to the problems with multiple threads -- the root cause is that http request callbacks and user interface events can come in an arbitrary order. This article works out an example that explains how this happens, as understanding the nature of asynchronous communication is the first step towards developing reliable apps.

Asynchronous communications in RIA's such as GWT and Silverlight force changes in the organization of software. Asynchronous Functions are a simple pattern that let you nest asynchronous calls.

Http responses in Silverlight (and other RIA languages) are asynchronous and need to be handled in callback methods. Where should the callback methods go? Bundling the start of an http call with the callback in a single Command object is a straightforward way to organize your code.