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# Friday, 20 July 2012

As announced by Scott Guthrie EF is today available as Open Source on Codeplex. As usual I had a first glance at the code to see what's inside. Is a big codebase as you can guess,but even with a first sight it is possible to spot some interesting things to learn. Here my list:

So nothing really complex, just good code snippets. Interesting, they internally uses XUnit for unit testing, not MSTest, and the framework for mocking is MoQ.

Friday, 20 July 2012 10:31:10 (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback
C# | CodeProject

# Monday, 25 June 2012

I recently started playing with stackexchange data. You can use that web app to look up existing queries created by other users or create your own, against any stackexchange site. If you are asking how you can obtain, for example, how many time a certain tag is viewed as a part of a question  to discover what’s ‘trendy’ if you think that the number of questions and aswers ( and the views count ) are meaningful by this point of view. If you think this is interesting you can leverage stackexchange data to extract almost whatever you want. Here below some example:

top 20 ‘Trending’ Tags in the last 30 days


Or if you are curious about your position in your country in term of reputation you can modify this query:

top 20 users classified by reputation in Italy


Monday, 25 June 2012 10:16:50 (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback

# Friday, 27 April 2012

I described the “typed factory” concept here some days ago. The solution we looked at was requiring the Castle DynamicProxy dependency. If you want something simpler zero dependency and “just working” I creted a little hacking factory: AnyFactory. It is really simple and does not requires any external dependency, and can be integrated in your project by just adding a single file. I provided some documentation on the project wiki. The extension works by crafting a factory implementation using Reflection.Emit. It does not requires to configure anything since a unresolved dependency satisfying some restrictive rule is considered to be a factory, and the implementation is produced in the background.

the rules for an interface to be consider a factory are:

  • It is a public interface
  • Each method name starts with Create
  • Each method return something
  • There is no properties

The name is required to begin with Create, if it contains something after Create, this is considered to be a named binding to solve. Construction parameters can be specified, but there is a restriction: the parameter name should match the implementation constructor parameter name. ANother limitation is that we don’t support the “delegate” factory.

Friday, 27 April 2012 16:54:54 (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback
C# | Programming

# Wednesday, 25 April 2012

Yesterday I had an interesting discussion with a colleague about using IoC in the real world in a proper way, without falling back in the Service Locator Antipattern, and of course without having a reference to the container, that is just so horrible to not worth any word. So we both found the solution being the use of factories, supplied by the container, to create the on-the-fly requested components. I was used to craft these factories by hand, but I know is a little silly, especially when the colleague talked about the Castle(Windsor) typed factories. So quite interesting, but since I choose NInject as my IoC ( Castle was the first container I saw, and my first love too ) I felt the challenge to implement the same but… Fortunately ( well, for say it would be nice being the implementer ) Remo Gloor provided a NInject extension that does almost the same for this other beautiful container. A nice documentation is also available on the Github repository. So thanks to a discussion I improved my programming knowledge, the Ninject.extensios.factoy is added to my toolbox A bocca aperta

Wednesday, 25 April 2012 15:58:04 (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback
CSharp | Programming

# Thursday, 12 April 2012

There are scenarios in which NHibernate performance decrease even if we do all the effort to correctly use it. This could happen if we need in some circumstances to load a lot of record ( I explicitly use record instead of ‘Entity’ ) from some relational structures, and doing this the OR/M way means overload the session with a lot of entities, that is painful in term of speed. Other cases happens when we need to  write or update something that is not properly represented in the entity model we have, maybe because the model is more “read” oriented. Other cases? I’m not able to grasp all  of course, but I’m sure that you face some if you use an OR/M ( not necessarily NH ) in your daily basis. Using NHibernate an alternative could be using FlushMode=Never in session, but you still have all the OR/M plumbing in the hydrating entity code that negatively impacts the performances. I obtained impressive results in solving such a situation, by using Dapper, a so called single file OR/M. It is a single file that provider some IDbConnection extension methods, those methods works on an already opened connection, so we can use the connection sticked to the NHibernate open session, as here below:

// don't get confused by LinqToNh Query<> this one is the Dapper query
// acting on the CONNECTION :)

session.Connection.Query<MyDto>("select Name=t.Name,Mail=t.Mail from mytable t where t.Valid=@Valid",new{Valid=true});

you obtain back a big recordset of MyDto instances in almost the same time if you wire by hand a DateReader vertical on the dto, with all the error checking.

So why don’t use it always?

Because despite the name Dapper is not an OR/M, it does not keep track of modified entities, it does not help you in paginating results or lazy load the entity graph, neither helps in porting from one SQL dialect to another.

Is this strategy used somewhere else?

You probably find interesting to read this post by Sam Saffron, this solution is used in combined with the LinqToSql OR/M to help when the OR/M performance are not enough.

By my test I experienced a performance increase of 10x in a very hacking situation, but I can’t show the case since it is not public code. Something more scientific about performance is here.

Thursday, 12 April 2012 09:41:12 (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback
CodeProject | Dapper | NHibernate | ORM

# Tuesday, 03 April 2012

I talked about this one file utility here and here. I decided the syntax I create in the last improvement, for allowing the user to customize the exception to throw was not so usable, so I modified it. Now the resulting code to throw a specific exception is:

        /// Classical not null verification, with custom 
        /// exception and message
        public void DoSomethingWithCustomMessage(string arg1)
            Contract.Expect(() => arg1)
                .Throw((n)=>new Exception(string.Format("I'm unhappy to see that {0} is null",n)))


So there is no more any magic formatting, we just need to provide a function returning some kind of exception. The lambda argument (n) is the literal representing the name argument. I also added a wiki page on the project repository, to show the basic usage of the library so at a glance you can see how it works.

Tuesday, 03 April 2012 07:55:51 (GMT Daylight Time, UTC+01:00)  #    Comments [0] - Trackback

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