Question

I can’t seem to access parent child child child. IE. WorkOrder has 1 Unit which has 1 Building which has 1 Site

I’ve been able to eager load the unit, but I can’t seem to get any “deeper”.

Code:

int workOrderId = 1;
var workOrder = context.WorkOrders.Expand("Unit").Where(w => w.Id == workOrderId).First();

string siteId = workOrder.Unit.Building.Site.Id.ToString(); // kaboom (null)

In theory I could eager load the WorkOrder unit, do the same with unit/building and then 1 more time with building to site. But that seems way overboard for what I’m trying to do.

I guess what I want to be able to do is expand all of the children in 1 query.

Any thoughts?

Answer 1

So here’s what I’ve found:

First off, WCF Data Services does not support lazy loading proof. This means that this code will never work:

var workOrder = context.WorkOrders.First();
string siteId = workOrder.Unit.Building.Site.Id.ToString(); // won't work w/ WCF Data Services

Then I thought I could use a join like below, however WCF Data Services does not support joins proof:

var query =
    from wo in context.WorkOrders
    join unit in context.Units on wo.Id equals unit.Id
    join building in context.Buildings on unit.Id equals building.Id
    join site in context.Sites on building.Id equals site.Id
    where wo.Id == workOrderId
    select new 
    {
        SiteId = site.Id,
    };

Finally, after taking a look at the oData specification of expand oData expand I was able to find that my original Expand usage was CLOSE to what I wanted, this works:

int workOrderId = 1;
var workOrder = context.WorkOrders.Expand("Unit/Building/Site").Where(w => w.Id == workOrderId).First();
string siteId = workOrder.Unit.Building.Site.Id.ToString(); // shows site id