Breeze does not expand a navigation property

问题

I have a Breeze dataservice (aka datacontext) in my Single Page Application. I want to get a list of Runs from a WebAPI controller along with a list of OutlineItems for each run.

The controller is returning the list of open Runs with child OutlineItems with this method on the BreezeController.

[AcceptVerbs("GET")]
public IQueryable<Run> Runs()
{
return _contextProvider.Context.Runs
    .Include("RunOutlineItems")
    .AsQueryable()
    .Where(r => r.RunStatusId < 4);    // 4 is the cutoff for open items             

}

Here is the data model.

namespace PilotPlantBreeze
{
    public class Run
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Rundate { get; set; }
        public DateTime? RunStart { get; set; }
        public int MachineId { get; set; }
        public int ProductId { get; set; }
        public int RunStatusId { get; set; }
        public string Comments { get; set; }

        // Nav props
        public IList<OutlineItem> RunOutlineItems { get; set; }
    }
}       

When I look at the Response data from the WebAPI request, the list of RunOutlineItems is in the JSON. Here is one item for example:

{
    "$id":"27",
    "$type":"PilotPlantBreeze.OutlineItem,PilotPlantBreeze.Model",
    "Id":22,
    "RunId":5,
    "TankId":4,
    "OutlineTopicId":1,
    "OutlineDescriptionId":9,
    "PersonId":1,
    "Value":"23"
}

Here is my client side javascript code to get the data from the WebAPI. Error checking and local cache checking omitted for clarity.

var getRuns = function () {
    // The EntityQuery is defined at the beginning of the dataservice
    //  Here I am asking for a query on the server.  Note the .expand 
    //  which is supposed to avoid lazy loading.  Lazy loading is turned off 
    //  on the WebAPI already.
    var query = EntityQuery
    .from("Runs")
    .expand("RunOutlineItems")
    .orderBy("rundate");

    // The manager is defined at the beginning of the dataservice
    //  Here I am asking the manager to execute the query with a promise
    return manager.executeQuery(query)
    .then(runsQuerySucceeded)
    .fail(runsQueryFailed);

    // The promise does not fail, but I would put an error in here if it ever does
    function runsQueryFailed(data) {
    }
    // When the promise succeeds, the data parameter is the JSON from the WebAPI
    function runsQuerySucceeded(data) {
        //
        // When I stop the debugger here data.results holds the entities, but
        //  the child entities for the RunOutlineItems is an observableArray with 
        //  nothing in it.
        //
        app.vm.runs.runs(data.results);
    }
};

So my question is how to get the child items into my viewModel. I have a workaround which gets the child Items in a separate call to the WebAPI on the server and processes them with a custom ko.bindHandler, but it would be convenient to have the navigation technology working.

回答1:

You shouldn't need both the 'include' (server side) and the expand (client side); either one should do the trick.

So I'd leave you client side query alone and modify the server side query to just this:

[AcceptVerbs("GET")]
public IQueryable<Run> Runs() {
    return _contextProvider.Context.Runs
      .Where(r => r.RunStatusId < 4);    // 4 is the cutoff for open items             

}

Note that the AsQueryable() is gone as well.

If this doesn't work, please post back.

来源：https://stackoverflow.com/questions/13943138/breeze-does-not-expand-a-navigation-property