Odata query won't expand

Question

I'm querying my service using a url like:

http://a.com:3080/odata/DiscussionVM(6)?$expand=Section,User

on controller method:

[EnableQuery(MaxExpansionDepth = 7)]
        public SingleResult<DiscussionVM> GetDiscussionVM([FromODataUri] int key)
        {
            return SingleResult.Create(db.DiscussionVMs.Where(discussionVM => discussionVM.DiscussionId == key));
        }

This works and returns the correct JSON.

However I then run the slightly more advanced query on a different model:

http://a.com:3080/odata/OrganisationVM(30)?&$expand=Categories($expand=Discussions($expand=Section,User))

and controller action:

// GET: odata/OrganisationVM(5)
        [EnableQuery(MaxExpansionDepth = 5, AllowedQueryOptions = AllowedQueryOptions.All)]
        public SingleResult<OrganisationVM> Get([FromODataUri] int key)
        {
            return SingleResult.Create(db.OrganisationVMs.Where(organisationVM => organisationVM.OrganisationId == key));
        }

this returns the below DiscussionVM JSON:

{
@odata.type: "#Models.DiscussionVM",
DiscussionId: 6,
Section_SectionID: 1005,
User_Id: "4cecc52e-ac3a-4696-ac6c-175af2a6378a",
DateCreated: "2014-12-06T00:00:00Z",
OrgCat_OrganisationCategoryId: 1,
Text: "Dummy section",
Html: null,
IsUserCreated: true,
Organisation_OrganisationId: null,
Positives: null,
Negatives: null,
CommentCount: 1
}

But contains no User or Section object. No error is thrown. The correct objects are queried (profiled) in the database and data including user and section are returned.

$expand=Categories($expand=Discussions($expand=Section,User($select=BLAH))) would throw an error stating User has no such property, and $expand=Categories($expand=Discussions($expand=Section,User($select=FirstName))) would succeed but the result would still have no User or Section. Deep inspection of the odata query parameters in the method shows that all expand options are present. This looks more and more like a problem with the serialization. — Jerther

Chtiwi Malek Chtiwi Malek · Accepted Answer · 2016-11-28T11:39:28

I discovred that oData needs the expanded entities to be referenced in its Edm Model. if not it will stop expanding after the first level, that's why further expands will not work.

Just add your expandable EntitySet to the ODataConventionModelBuilder in your IEdmModel (in MapODataServiceRoute's model config) :

var builder = new ODataConventionModelBuilder();
// ...
builder.EntitySet<Categories>("categories");
// ...

Hope this helps.

Odata query won't expand

3 Answers