Accessing Parent object from ChildAccessing Parent object from Child
Old forum URL: forums.lhotka.net/forums/t/267.aspx
Pradeep posted on Sunday, June 04, 2006
Hi,
I have a Company Parent Object and this has a Contact List, which is a collection of Contact objects.
Company and Contact are root level objects (similar to project and resource in the book sample) and Contact object has a company name property. When I try to add a contact to a company, I want to have a validation rule, making sure that the contact's company name is same as the Company's name property.
To keep it short. I want to get the Parent of Contact object (ContactList) and then get to its parent (Company) and check for the Name property. But BusinessCollectionBase does not have a parent property.
Could any one tell me, how to get to the parent object (in this case, Company).
Thank You
xal replied on Sunday, June 04, 2006
Declare a parent field inside your collection like this:
<NonSerialized(), NotUndoable()> Private mParent as Company
Now, you can have a method like:
SetParent(parent as Company)
You should call that method when you make an instance of the collection and when your root object is desserialized.
You can expose mParent through a readonly property.
Andrésxal replied on Sunday, June 04, 2006
You could also just have a string field (that would use the same technique for setting / reading) inside your collection that you can assign from the parent whenever the company name changes. This would of course be much simpler.
AndrésPradeep replied on Monday, June 05, 2006
Thanks for your suggestion. I tried the first one. But I didn't set the parent before adding the child to the collection. So it was throwing error. Now, I am just using one more property and comparing with it (as your second sugg.).
I posted this here, just to make sure that I didn't miss any obvious method and doing it in a round about way. Also in VB6.0 version of CSLA it had parent object.
Thanks again.
Crestline replied on Tuesday, June 20, 2006
In our scenario we need access to the parent's ID so that when the
child's data is saved out, one of the values needed to store in the
Child's table is the related ID of the parent.
How should we go about getting the parent's ID?
Outline:
Categories EditableRootList
Category EditableRoot
SubCategories EditableChildList
SubCategory EditableChild
UI
We have a form containing 2 datagrids. The Category grid and the
related SubCategory grid. Both Categories and SubCategories are
editable on this form. In the underlying data tables on the
server, there is an CategoryID field in the SubCategory table so that
we can see the given subcategories for any particular category.
This is pretty straight forward stuff, nothing out of the ordinary.
Question
When save is clicked on the form, the Categories.Save() method is
called which of course saves both Categories and SubCategories.
How do we set the CategoryID value of the SubCategories if we can't get
to the parent object to find it?
Maybe our model is wrong but we are definately looking for some suggestions. Any thoughts?
Thanks,
BR
JoeFallon1 replied on Tuesday, June 20, 2006
In my collections I use:
Protected Friend Overridable Sub Update(ByVal tr As IDbTransaction, ByVal parent As MyParent)
....
For Each child In List
child.Update(tr, parent)
Next
....
Then in the child BO I use:
The only method that requires the Parent is the Insert.
Protected Friend Overridable Sub Update(ByVal tr As IDbTransaction, ByVal parent As MyParent)
...
(I call a method like InsertData rather than write all the code in one large Update section.)
Protected Overridable Sub InsertData(ByVal tr As IDbTransaction, ByVal parent As MyParent)
DAL.ExecuteNonQuery(tr, CommandType.Text, SQL.Insert(parent.key,... ))
I use Codesmith templates to generate all this for me.
HTH
Joe
Crestline replied on Wednesday, June 21, 2006
Thanks Joe,
We implelemented something before I read your reply. I'll take a look at your suggestion.
BR
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