LINQ to SQL (Part 4 - Updating our Database)
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by Scott Guthrie
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Custom Entity Insert/Update/Delete Method Validation

There are times when you want to add validation logic that is specific to insert, update or delete scenarios.  LINQ to SQL in Beta2 enables this by allowing you to add a partial class to extend your DataContext class and then implement partial methods to customize the Insert, Update and Delete logic for your data model entities.  These methods will be called automatically when you invoke SubmitChanges() on your DataContext.

You can add appropriate validation logic within these methods - and if it passes then tell LINQ to SQL to continue with persisting the relevant changes to the database (by calling the DataContext's "ExecuteDynamicXYZ" method):

Figure 15

What is nice about adding the above methods is that the appropriate ones are automatically invoked regardless of the scenario logic that caused the data objects to be created/updated/deleted.  For example, consider a simple scenario where we create a new Order and associate it with an existing Customer:

Figure 16

When we call northwind.SubmitChanges() above, LINQ to SQL will determine that it needs to persist a new Order object, and our "InsertOrder" partial method will automatically be invoked. 


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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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