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的项目数，但是在'skip'和'top'之前。

我已经尝试在url（https://damienbod.wordpress.com/2014/06/13/web-api-and-odata-v4-queries-functions-and-attribute-routing-part-2/ - “$ count的示例”）的查询选项中传递'$ inlinecount = allpages'和'$ count = true'参数，但我的WebAPI响应总是只有查询结果（集合） - 整个响应看起来像：

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

回复中没有类似“odata.count”的内容。

我还尝试在我的WebAPI控制器操作中返回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），但不推荐使用Request.GetInlineCount（），其值始终为null。

有什么想法吗？

[更新]我刚刚发现了同样的问题：WebApi with Odata NextPage and Count not appearing in the JSON response我删除了[EnableQuery]属性，现在我的回复如下：

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

但仍然“Count”始终为null。：（

<小时/> 编辑：调试并在我的控制器中的Request属性中搜索计数值后，我发现正确的Count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此值，我的控制器看起来像这样：

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);
}

它工作正常，但我仍然不知道为什么我必须使用这样的解决方法。

Answer 1

供将来参考（OData v4）：

首先$inlinecount OData v4不支持$count=true，因此您应该使用ApiController。

其次，如果你有一个正常的IQueryable<T>，并且你返回类似count的类型，这就是你可以将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)); }属性附加到返回结果的方式：

ApiController

注意： count s不支持OData功能不能包含$metadata或ApiController之类的内容。如果你选择使用简单count上面的方法是你应该使用的方式返回ODataController属性。

要完全支持OData功能，您应该通过以下方式实现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); } }：

<强> PeopleController.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; }

App_Start \ WebApiConfig.cs

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

然后以这种方式访问您的OData Api（示例）：

编码的uri：

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

解码：

CREATE TABLE public.portfolio ( id INTEGER PRIMARY KEY NOT NULL DEFAULT nextval('portfolio_id_seq'::regclass), name CHARACTER VARYING(80) NOT NULL, path CHARACTER VARYING(80) NOT NULL ); CREATE UNIQUE INDEX portfolio_path_key ON portfolio USING BTREE ("4"); CREATE UNIQUE INDEX portfolio_name_key ON portfolio USING BTREE (name);

参考文献：

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

Answer 2

这就是我使用的oData v4：

Request.ODataProperties().NextLink, 

Request.ODataProperties().TotalCount

Answer 3

请您在https://github.com/OData/ODataSamples/blob/master/Scenarios/TripPin查看示例服务TripPin web api实施。您可以按照机场控制器中的代码和代码http://services.odata.org/TripPinWebApiService/Airports的服务进行操作？$ count = true可以正确返回计数。

Answer 4

这也可以通过动作过滤器来实现：

/// <summary>
/// Use this attribute whenever total number of records needs to be returned in the response in order to perform paging related operations at client side.
/// </summary>
public class PagedResultAttribute: ActionFilterAttribute
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="actionExecutedContext"></param>
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        base.OnActionExecuted(actionExecutedContext);
        if (actionExecutedContext.Response != null)
        {                
            dynamic responseContent=null;
            if (actionExecutedContext.Response.Content != null)
                responseContent = actionExecutedContext.Response.Content.ReadAsAsync<dynamic>().Result;
            var count = actionExecutedContext.Response.RequestMessage.ODataProperties().TotalCount;
            var res = new PageResult<dynamic>() {TotalCount=count,Items= responseContent };

            HttpResponseMessage message = new HttpResponseMessage();
            message.StatusCode = actionExecutedContext.Response.StatusCode;

            var strMessage = new StringContent(JsonConvert.SerializeObject(res), Encoding.UTF8, "application/json");
            message.Content = strMessage;
            actionExecutedContext.Response = message;               
        }           
    }
}

自定义PageResult类是：

public class PageResult<T>
{      
    public long? TotalCount { get; set; }
    public T Items { get; set; }
}

用法：

[PagedResult]
[EnableQuery()]

OData v4 Web API响应中的项目计数

4 个答案: