Items count in OData v4 WebAPI response

Question

How to return number of items in OData v4 HTTP response?

I need this number to pagination, so it should be number of items after filtering, but before \'skip\' and \'top

Answer 1

For future reference (OData v4):

First of all $inlinecount it's not supported in OData v4 so you should use $count=true instead.

Second, if you have a normal ApiController and you return a type like IQueryable this is the way you can attach a count property to the returned result:

using System.Web.OData;
using System.Web.OData.Query;
using System.Web.OData.Extensions;

//[EnableQuery] // -> If you enable globally queries does not require this decorator!
public IHttpActionResult Get(ODataQueryOptions queryOptions)
{
    var query = _peopleService.GetAllAsQueryable(); //Abstracted from the implementation of db access. Just returns IQueryable
    var queryResults = (IQueryable)queryOptions.ApplyTo(query);
    return Ok(new PageResult(queryResults, Request.ODataProperties().NextLink, Request.ODataProperties().TotalCount));
}

Note: OData functionality does not supported by ApiControllers so you cannot have things like count or $metadata. If you choose to use simple ApiController the way above is the one you should use to return a count property.

---

For a full support of OData functionality you should implement a ODataController the following way:

PeopleController.cs

using System.Web.OData;
using System.Web.OData.Query;

public class PeopleController : ODataController
{
    [EnableQuery(PageSize = 10, AllowedQueryOptions = AllowedQueryOptions.All)]
    public IHttpActionResult Get()
    {
        var res = _peopleService.GetAllAsQueryable();
        return Ok(res);
    }
}

App_Start \ WebApiConfig.cs

public static void ConfigureOData(HttpConfiguration config)
{
    //OData Models
    config.MapODataServiceRoute(routeName: "odata", routePrefix: null, model: GetEdmModel(), batchHandler: new DefaultODataBatchHandler(GlobalConfiguration.DefaultServer));
    config.EnsureInitialized();
}

private static IEdmModel GetEdmModel()
{
    var builder = new ODataConventionModelBuilder
    {
        Namespace = "Api",
        ContainerName = "DefaultContainer"
    };
    builder.EntitySet("People").EntityType.HasKey(item => item.Id); //I suppose the returning list have a primary key property(feel free to replace the Id key with your key like email or whatever)
    var edmModel = builder.GetEdmModel();
    return edmModel;
}

Then you access your OData Api this way (example):

encoded uri:

http://localhost:/People/?%24count=true&%24skip=1&%24top=3

decoded:

http://localhost:/People/?$count=true&$skip=1&$top=3

References:

• How to Use Web API OData to Build an OData V4 Service without Entity Framework
• Web API OData V4 Pitfalls
• Create an OData v4 Endpoint Using ASP.NET Web API 2.2