oData filter on array element

Question

I wanted to know if it was possible to filter on a specific array element. I know that it is possible to filter on nested properties and to apply any/all functions on collections, but didn't find any documentation on how to filter on specific index on collection. As an example (expressed in Linq):

data.Where(d => d.Proposals[0].Growth.Value == 0.05m)

I'm expecting a syntax like:

$filter=Proposals(0)/Growth/Value eq 0.05M

lencharest · Accepted Answer · 2016-01-04 20:30:58Z

2

OData is based on the Entity Data Model, which does not support ordered collections (arrays). So there is no built-in syntax for filtering by position.

If your goal is to filter against a default Growth/Value using a client-supplied value, you can achieve that with an OData function. Declare the function in your Web API config.

// builder is an instance of ODataConventionModelBuilder
var defaultGrowthValueFunction = builder.EntityType<Zebra>().Collection.Function("WhereGrowthEquals");
defaultGrowthValueFunction.Parameter<decimal>("value");
defaultGrowthValueFunction.ReturnsCollectionFromEntitySet<Zebra>("Zebras");

The function is named WhereGrowthEquals and it is bound to the Zebras entity set. (I've invented an entity type named Zebra to host the Proposals array from your example above.)

Now define the function in the ZebrasController. (For testing, I defined a static list of Zebra instances named AllZebras.)

public class ZebrasController : ODataController
{
    [HttpGet]
    [ODataRoute("Zebras/Default.WhereGrowthEquals(value={value})")]
    public IHttpActionResult WhereGrowthEquals(decimal value)
    {
        return this.Ok(AllZebras.Where(z => z.Proposals[0].Growth.Value == value));
    }
}

Note that the bound function is namespace-qualified in the ODataRoute attribute. (Default is the default namespace name.)

Finally, invoke the function from the client as follows.

GET http://hostname/Zebras/Default.WhereGrowthEquals(value=0.05)

answered Jan 4, 2016 at 20:30

lencharest

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2 Comments

enenkey Over a year ago

Thank you for your detailed answer. Actually I need to express the filter request in a generic way, I can't implement specific filtering on the server side. I mean the requests are to be generated by a client grid depending on the shown columns and those columns are a projection of complex objects (including arrays). I could have another columns referencing a path like Proposals[1].AnotherArray[2].Amount.Value. So, I'm looking for a standard and generic syntaxt to express that path in OData query.

lencharest Over a year ago

Hmmm. I'm curious as to how you are modeling the arrays. What does your $metadata doc look like?

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