LINQ to SQL (Part 4 - Updating our Database)
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by Scott Guthrie
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Advanced: Looking at the Entire Change List for the Transaction

There are times when adding validation logic can't be done purely by looking at individual insert/update/delete operations - and instead you want to be able to look at the entire change list of operations that are occurring for a transaction. 

Starting with Beta2 of .NET 3.5, LINQ to SQL now enables you to get access to this change list by calling the public DataContext.GetChangeList() method.  This will return back a ChangeList object that exposes collections of each addition, removal and modification that has been made. 

One approach you can optionally employ for advanced scenarios is to sub-class the DataContext class and override its SubmitChange() method.  You can then retrieve the ChangeList() for the update operation and perform any custom validation you want prior to executing it:

Figure 17

The above scenario is a somewhat advanced one - but it is nice to know that you always have the ability to drop-down and take advantage of it if needed.


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User Comments

Title: Good Article   
Name: Vishnu Shanmugam
Date: 2010-12-11 12:46:40 AM
Comment:
Excellent article.
Title: very clear   
Name: tarun
Date: 2010-08-13 7:31:17 AM
Comment:
thanks for the clear explanation
Title: this is terrible   
Name: mac
Date: 2010-08-02 4:56:22 PM
Comment:
this is by far the worst display of CRUD i have seen yet.
Title: How can I insert dates   
Name: Ernie Smart
Date: 2010-03-17 1:08:05 PM
Comment:
How can I parse or convert dates? Let's say I have a text box (txtDate) to enter the dates and the database has a field called OrderDate. If either of the follwoing two:
OrderDate = Convert.ToDateTime(txtDate)
OrderDate = DateTime.Parse(txtDate)
I get System.FormatException: String was not recognized as a valid DateTime error.
If I do OrderDate = DateTime.Now, the code executes correctly.
How can convert the date entered in the text box so the program will work?
Thanks
Title: i can't find add,update or delete methods for my data context.   
Name: Enow Mbi
Date: 2010-02-19 11:10:15 AM
Comment:
GREAT ARTICLE.
I can't figure out why i can't find,add,update or delete methods of my data context despite the fact that my table has a primary key.
Title: More Article   
Name: twinsf
Date: 2010-01-28 2:09:59 AM
Comment:
thank youu for helpfull
Title: Bad advice   
Name: Simon
Date: 2008-12-28 11:59:06 PM
Comment:
The partial class validation logic you demonstrate is not testable and is therefore useless to me. Isn't it better advice to put the validation logic in business objects (as Rocky Lhotka would urge). Or alternatively, to put it in a service layer or repository that is testable. Baking your validation logic into these proprietary, tightly coupled, LINQ DTOs seems wrong.
Title: Create items together   
Name: Tom
Date: 2008-12-24 1:49:56 PM
Comment:
Is there a way to create a category and product together? From what I've seen, beverages.Products would be null, so you can't call "Add" on it. You also can't set Products equal to a new EntitySet, because the setter assumes a non-null EntitySet already which it calls "Assign" on.

Thanks!
Title: Very helpful   
Name: Alexander
Date: 2008-11-13 9:20:30 PM
Comment:
Just great. Killed a few days with msdn stuff trying to comprehend logic of Entity Insert/Update/Delete customisatiton. Just got it from this article in a couple of minutes.
Thank you.
Title: Linq doesn't update   
Name: Moez Tounsi
Date: 2008-10-07 12:15:53 PM
Comment:
Following the example above, ling will add a new record with the new parameters.
We have to handle the deletion of the old element.
Title: Excellent   
Name: Wayne
Date: 2008-07-23 12:27:59 AM
Comment:
Excellent article, Well done, a really good read.
Title: Thanks a lot   
Name: Andi
Date: 2007-12-02 11:25:10 AM
Comment:
Thank you for this great article!!!






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