Linq To SQL and Change Tracking

I have been using Linq To SQL in a project recently. Linq is a great way to traverse through a collection of objects. Its a very nice utility and can get rid of those unsightly nested foreach loops with if/elses in your code. Linq To SQL is also a nice basic Object Relational Mapper. The issue is "when the rubber meets the road", as it were. Linq seems a slight bit incomplete. Take this example:

A simple ChangeLog class. It has an Enum ChangeLogStates that has 4 states, Created, Modified, StatusChanged (a disposition), Shelved(basically deleted). Now, i could do an ChangeLog.add(LogStates.Created/Modified/Changed/Shelved,Object Key, strDescription) to every line of code where there is a change in the database....everywhere i insert, update the underlying entity. But Using the beauty of OOP and Linq to SQL, i can impletement the Datacontext's insert and update partial methods:
partial void insertLinqItem(LinqItem item);
partial void updateLinqItem(LinqItem item);

insertLinqItem works great!

partial void insertLinqItem(LinqItem item){



ChangeLog.add(ChangeLogState.Created, item.ID, string.format("New Item was created with ID:{0}", item.ID));



}

the problem lies with the other statuses!

partial void updateLinqItem(LinqItem item){





//TODO: how in the world do i find out if the item has been changed



//Done: I can check  if the current status is Shelved

if(item.status ==  "shelved"){

ChangeLog.add(ChangeLogState.Shelved, item.ID, string.format("Item  {0} was Shelved", item.ID));

}

//else if(item.oldstatus != item.newstatus? || item.newstatus.isdirty?

//TODO: How do i tell if a specific property item.status has been changed?!

//ChangeLog.add(ChangeLogState.StatusChanged, item.ID, string.format("Item's Status was changed from {0} to {1}", item.oldstatus, item.newstatus));

}



//DONE: I can Tell when any other property other than status has been changed.....

ChangeLog.add(ChangeLogState.Modified, item.ID, string.format("Item {0} was modified", item.ID));

}


Linq doesnt do change tracking! I was shocked. There is an IsDirty or HasChanged property. Datasets have a DiffGram concept that allows you to check the changes that have happened during the lifetime of the dataset. What happened? Luckily i can pepper my code with changelog lines everywhere an entity has been changed, but why cant i just use the OOP way? I'd have to create a change tracking framework!


Anyhow, Sorry for the simplistic example, There is a great blog entry on Change tracking in Linq by Freek Leemhuis. Visit for More information and other links.

Comments

Post a Comment

Popular posts from this blog

Quick Progress!

Parsing for fun and profit I remember creating parsers to be a bit harder. I tried using Antlr when doing the JavaFX DLR project and failed at it miserably. It felt messy. I couldnt get a feel for how to structure the document, etc. I was drawn to the Irony parser framework because declaring the grammar in C# somehow felt (at the time) cleaner and it seemed to allow for more expressive statements and character logic. I am not sure if it was my previous experience with parsing and Antlr (or Irony), or how clean and expressive the GOLD parser framework is, but I've been able to create a working parser in just a few days of coding. And by working, I mean it parses and understands valid LLVM IR straight from the project's documentation:  I actually implemented a a lot more operations and keywords needed to parse the example. It was just easier that way. I am going to now start building an AST. I've decided to be a bit aggressive because I think the AST will drive ...
Read more

Its Happening! Its really Happening! ^_^

So, big news. The Oculus/Facebook folks just announced that all kickstarter backers who got a unit, will get a commercial unit!  As, an original backer of the Oculus (and one of the backers who was actually ok with the facebook purchase), I am extremely happy, and extremely proud/humbled that I was a part of helping VR come back.  Big Thank you to the folks at Oculus! As a small token of our appreciation for your support, all Kickstarter backers who pledged for a Rift development kit will get a free Kickstarter Edition Oculus Rift! And like all Rift pre-order purchasers, you’ll receive a bundled copy of Lucky’s Tale and EVE: Valkyrie. To claim your free Rift, fill out the survey you’ll receive from Kickstarter before February 1, 2016 and provide a shipping address that is located in one of the 20 countries Rift is launching in. For those who don’t live in one of those 20 countries, we’re working on an alternative, and you can let us know your preference in the for...
Read more
So I've again been bitten by the Transcoding/transpiling bug...Doh! My history with Transcoding  A few years back (around mid-2007), I was enamored with a new language on the block, JavaFX (now vala). Alas, I had moved on from the Java platform to the .Net platform during that time, and Silverlight just hit the stage (and WPF). I was more of a fan of the declarative and expressive nature of JavaFX than I was of XAML, so I looked into porting JavaFX script to the .Net platform (and later the DLR). I halted my work in 2008-2009, as JavaFX script was dying, and the Parser technology I was using (a great C# based parser called Irony) was giving me issues when integrating with the DLR. The LLVM Project I've been a fan of the LLVM project since about 2009. I have also watched its MSIL backend go into disrepair and interest in C# as part of the vmkit wane. I answered some stack overflow questions in 2011 about this http://stackoverflow.com/questions/5054938/how-to-translate...
Read more