ASP.NET and F# (I.) - Creating MVC web applications in F#

Some time ago, I wrote a couple of examples of developing web applications in F# using ASP.NET. Since then, the F# language and runtime has changed a little bit and there are also new technologies available in ASP.NET, so I thought I'd write a more up-to-date article on this topic. In this article, I'll present a simple "demo" F# web application that you can use as a starting point when creating your own projects (you'll also find a convenient Visual Studio 2010 template below). The article shows the following interesting things:

• ASP.NET MVC - We're going to use ASP.NET MVC Framework to create the web application. As the article name suggests, most of the actual program code including models and controllers will be implemented in F#.
• F# LINQ to SQL - The application uses a sample Northwind database and we'll write queries for selecting data from the database using LINQ support that's available in the F# PowerPack.
• F# features - The application also uses some nice F# features that are quite useful for developing web applications. We'll use modules and records to implement the model and we'll also use advanced meta-programming features for constructing LINQ queries.

If you want to use F# for creating an MVC application, you have a few options. It should be possible to create the web application solely as an F# project. However, we'll use a more convenient approach. We'll create a standard C# MVC project and move all the actual implementation to an F# library. We'll look at the application structure shortly. The following screenshot shows a page that lists products in the Northwind database:

CLinq - LINQ support for the C++/CLI language

I started working on this project, because I attended C++ class at our university and I had to do some application in C++. Because I hate doing useless projects I wanted to work on something interesting and so I started thinking whether it would be possible to enable LINQ support in C++/CLI...

C++/CLI is a very flexible language and the following example proves that enabling LINQ support in C++/CLI isn't impossible. The following database query returns name of contact and company for all customers living in London:

// create connection to database
NorthwindData db(".. connection string ..");

// declare database query
Expr<Customers^> cvar = Var<Customers^>("c");
CQuery<String^>^ q = db.QCustomers
  ->Where(clq::fun(cvar, cvar.City == "London"))
  ->Select(clq::fun(cvar, 
      cvar.ContactName + Expr<String^>(", ") + cvar.CompanyName));

// execute query and output results
for each(String^ s in q->Query)
  Console::WriteLine(s);

If you are interested in more information about CLinq project you can...

• .. continue and read the entire article
• Visit the CodePlex project homepage [^]

Aho-Corasick string matching in C#

I implemented this algorithm because I worked on one project where we needed to filter bad language in comments submited by users (You wouldn't believe what anonymous users sometimes write). First I tried simple solution using String.IndexOf and using Regex, but none of these solutions was very suitable for this problem, so I decided to implement Aho-Corasick algorithm which is probabbly the best algorithm for this purpose.

Article (published here an on CodeProject.com) describes implementation of this algorithm for pattern matching. In simple words this algorithm can be used for searching text for specified keywords. This implementation is usefull when you have a set of keywords and you want to find all occurences in text or check if any of the keywords is present in the text. You should use this algorithm especially if you have large number of keywords that don't change often, because in this case it is much more efficient than other algorithms that can be simply implemented using .NET class library.

Aho-Corasick search algorithm is very efficient if you want to find large number of keywords in the text, but if you want to search only for a few keywords it is better to use simple method using String.IndexOf.

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