count - OData v4 WebAPI 响应中的项目计数

Question

如何返回 OData v4 HTTP 响应中的项目数？

我需要这个数字来分页，所以它应该是过滤后、“跳过”和“顶部”之前的项目数。

我已经尝试在 url 的查询选项中传递 '$inlinecount=allpages' 和 '$count=true' 参数(https://damienbod.wordpress.com/2014/06/13/web-api-and-odata-v4-queries-functions-and-attribute-routing-part-2/ - “$count 的示例”)，但我来自 WebAPI 的响应始终只有查询结果(集合) - 整个响应如下所示:

[
    {
        "Name":"name1", 
        "age":5
    }, 
    {
        "Name":"name2", 
        "age":15
    }
]

响应中没有类似“odata.count”的内容。

我还尝试在 WebAPI Controller 操作中返回 PageResult 而不是 IQueryable(如此处所述: http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/supporting-odata-query-options#server-paging )，但 Request.GetInlineCount() 已弃用，并且其值始终为 null。

有什么想法吗？

[更新]我刚刚在这里发现了同样的问题:WebApi with Odata NextPage and Count not appearing in the JSON response我删除了 [EnableQuery] 属性，现在我的响应如下所示:

{
    "Items":
    [
        {
            "Name":"name1", 
            "age":5
        }, 
        {
            "Name":"name2", 
            "age":15
        }
    ],
    "NextPageLink":null,
    "Count":null
}

但“Count”仍然始终为空。 :(

<小时/> 编辑:在 Controller 的请求属性中调试和搜索计数值后，我发现正确的计数值位于名为“System.Web.OData.TotalCount”的属性中。所以现在我从该请求属性中提取该值，我的 Controller 如下所示:

public PageResult<People> Get(ODataQueryOptions<People> queryOptions)
{
    var query = _context.People.OrderBy(x => x.SomeProperty);
    var queryResults = (IQueryable<People>)queryOptions.ApplyTo(query);
    long cnt = 0;
    if (queryOptions.Count != null)
        cnt = long.Parse(Request.Properties["System.Web.OData.TotalCount"].ToString());

    return new PageResult<People>(queryResults, null, cnt);
}

它工作得很好，但我仍然不知道为什么我必须使用这样的解决方法。

Answer 1

供将来引用(OData v4):

首先$inlinecount OData v4 不支持它所以你应该使用$count=true相反。

第二，如果你有正常的ApiController然后您返回类似 IQueryable<T> 的类型您可以通过这种方式附加 count返回结果的属性:

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<People> queryOptions)
{
    var query = _peopleService.GetAllAsQueryable(); //Abstracted from the implementation of db access. Just returns IQueryable<People>
    var queryResults = (IQueryable<People>)queryOptions.ApplyTo(query);
    return Ok(new PageResult<People>(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.

<小时/>

为了完全支持 OData 功能，您应该实现 ODataController方法如下:

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>("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;
}

然后您可以通过以下方式访问 OData Api(示例):

编码后的 uri:

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

解码:

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

引用文献:

• 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