Join support

[JDT]

Please include LINQ join support for querying multiple objects. For example. This is HUGE for us.

pseudo

var result = from n in IScope.extent<customer>()

JOIN o in IScope.extent<office>() 

where c.officeId = o.id

Thanks!

[Thomas]

Hi JDT,

normally you should be able to just follow the reference on the Customer instance (the rev-engineering wizard should have created such a reference from Customer to Office). By following this reference, OpenAccess generated the needed joins internally. You can simply perform a linq query for the customer

var res = from c in scope.Extent<Customer> select c


Best wishes,
Thomas
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[Phil]

I second the request that JOINs are required.  As far as I can tell, OpenAccess will only generate the right joins if your database uses Foreign Keys to enforce Reference Integrity.  Ours, instead (for various reasons), uses triggers to enforce RI and so the relationships between tables isn't know to OA. 

[Alexander]

Hello Phil,

You can manually define the necessary relations using the Reverse mapping wizard. For the example you provided the steps would be as follows:

• Open the Advanced View tab in the Reverse mapping wizard;
• Select the class Customer from the treeview;
• Click the Create Ref button;
• Set an appropriate name for the reference (like Office) and choose the Office class from the Type combobox;
• The first column (Field) in the grid below should now have a value (Office.id). Click on the blank field in the second column and from the combobox select the officeId field.
• Save the configuration and generate the classes;

Now you should be able to access the Office object directly from the Customer using the Customer.Office reference. Hope that helps.
Greetings,
Alexander
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[JDT]

That works, but what if we want to be able to build and run those queries on the fly? In our case we would have to go create a ton of references which is a pretty big project. Like Phil our relationships aren't set as FK, or enforced by the schema.

Thanks.

[Alexander]

Hello JDT,

I am afraid this is not possible at the moment. Theoretically you should be able to execute SQL statements with JOINs using the ObjectScope.GetSqlQuery() method, but the result would be an object array which is not very easy and type-safe to work with. However, the Linq support for Joins is scheduled for the Q3 release this year.

All the best,
Alexander
the Telerik team

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