Mapping single class with a table was bit easy and fun. Next should be mapping associations, first I will try to map a simple one, using our existing application code. A person can have multiple email addresses.
So here is the modified code for person
In my previous post I generated a database without any mapping or customization, I got what Entity Framework could coerce from my class. Look at the schema which was generated.
Let’s see what I did not like about this.
- table name is not what I like to have
- Id was not marked as identity column, so no auto generation for this column
- all alphanumeric columns are created using nvarchar(MAX) which is not good too
- and the last, I wanted to use only date for birthdate not datetime
I was working on a personal project today, and did a lot of experiments on Code First Model with Entity Framework. All of these were quite amazing and revealed a lot of underlying implementation and how things have progressed in Entity Framework world. I looked at various articles which helped me understand all these aspects, and am grateful of all of them. So I thought why not write some posts of mine too, just to document what I have learned, so that others might benefit from it too.
For that purpose I am starting with a simplest item, I will try to generate a database for a single class, and see how it looks. By the way I am using Entity Framework 5.
Here is the class, which I will work on.
Today I was helping on a project which was using ADO.NET SQL Client. Wow, it looks so much scary, and old. I was asked to do some tweaks, so that data layer could be organized. Can I use Repository pattern here, one of the ways to add separation of responsibility these days.
So I started on creating a base class for these repositories. I thought of managing all connection related code in that base class. That was quite easy when I moved ExecuteNonQuery related calls here. Next came the hardest part ExecuteReader, how to send back DataReader without loosing control on my connection state. I can not move all reader related usage in base class, that would negate single responsibility rule.
Hmm, one way would be to create a virtual method in base class, and then each inherited class can override and implement it’s own mapping rules in it. I did small test with that, but soon was struck, what about mapping compositions. If I used this approach then I will have to add multiple conditional cases to map each item properly.
Then I thought of passing in mapper related methods as delegate, not bad. But why not use new concepts, Action<T, T …> / Func<T, …, TResult> / Predicate<T, …, bool>.
Installing any application is not a hard part, but preparing your system for that installation takes some time and considerations. While installing Foundation today, I had the same issue myself. I did not know which pre-requisites should be installed first. I searched for it, and found different combinations, but one told me to run the pre-requisite installer first, it will let you know what are missing for you. Here are those which were required on my machine.
For some you will have to look for the specific download for your operating system (x86 / x64).
I downloaded and installed them, and was able to proceed next. By the way, did I mentioned that I am using Windows Server 2008 R2 Standard with Service Pack 1.
UPDATE: I found a PowerShell script for downloading all these pre-requisites, grab it from here, it might be handy too. http://gallery.technet.microsoft.com/office/bcf3332d-f726-4ac7-b01a-eeda4b7ece8e