N.B.Throughout this post I am using Excel 2010 and Visual Studio 2010.

Writing a UDF in VBA to be exposed to Excel cells is straight forward, just write the function in a VBA module and Bob’s your uncle. However, it is slightly trickier to expose your functions to Excel in a managed language, such as C# or F#.

Read the rest of this entry »

Speaking to the developers about JustGiving’s RESTful APIs

Charity Hack is an annual event held and sponsored by PayPal UK at their venue in Richmond, London on a Saturday and a Sunday. It is an event where developers from different backgrounds are invited and introduced to different charity-relaled organisations APIs where developers are encouraged to hack useful apps using these APIs.

We introduced, as JustGiving, our new RESTful APIs and demonstrated how to use them.

Having a discussion with JustGiving developers (back to camera)

Working with other colleagues, I found these C# syntaxes are still not well-known and used, so I thought of blogging on them.

1 – Properties Without Members

In the old days, before C# 3.0, we used to write syntax like:

Read the rest of this entry »

I have explained in The Three Steps of Building an ASP.NET Validator Control, how to build a validator control from the ground up in three easy steps and in a reusable format. I highly recommend reading it before going any further.

Here I am discussing the common validator control security holes that might compromise your forms security when left untreated.

Read the rest of this entry »

The standard ASP.NET validator controls such as the RequiredFieldValidator or the RegularExpressionValidator do not cover all validation requirements, so usually developers tend to create a CustomValidator for such scenarios.

A major problem with the CustomValidator is reusability, as if you wanted to use the validator in another project then there would be some copying and pasting and code duplication, then you have to maintain multiple versions of the same control.

The solution, as you have guessed from the title, is to build your own validator control when possible to promote reusability.

In this post I will be showing you in three simple steps how to build an ASP.NET validator control and take credit card number format check to show by example. I will also be building the architecture so that your validator and other validators that you will develop in the future could be as reusable as possible.

How to Check a Credit Card Format

Luhn check is an algorithm that checks if a credit card number is valid (format wise), so in practice, before you even think of doing any further processing on the credit card, this check should be satisfied.

Read the rest of this entry »