Question

我正在通过利用LINQPad查询现有的OData饲料,了解OData。利用Netflix馈赠,我试图获得一份获赔最多的行动者名单,但我正在经历奇怪的例外。我的第一次尝试是:

People.OrderByDescending(p => p.Awards.Count).Take(10)

但是,这给我一个<代码>5Dataservice QueryException,但内有例外:

没有财产类型 System.Collections.Generic.ICollection'1[[Netflix.Catalog.v2.Entities]。标题Award, Netflix.Catalog.v2, FCCC/SBI/2007/8, 第7页。

我试图用<代码>.Count()推广方法而不是<代码>来改变情况。不动产:

People.OrderByDescending(p => p.Awards.Count()).Take(10)

但是,这只是玩:,我是英瓦利德卡斯特约会:

Unable to cast object of type System.Linq.Expressions.PropertyExpression to type System.Data.Services.Client.ResourceExpression .

at System.Data.Services.Client.ResourceBinder.AnalyzeCountMethod(MethodCallExpression mce)
at System.Data.Services.Client.ResourceBinder.VisitMethodCall(MethodCallExpression mce)
at System.Data.Services.Client.ALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.DataServiceALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.ALinqExpressionVisitor.VisitLambda(LambdaExpression lambda)
at System.Data.Services.Client.ALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.DataServiceALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.ALinqExpressionVisitor.VisitUnary(UnaryExpression u)
at System.Data.Services.Client.ALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.DataServiceALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.ALinqExpressionVisitor.VisitExpressionList(ReadOnlyCollection1 original) at System.Data.Services.Client.ALinqExpressionVisitor.VisitMethodCall(MethodCallExpression m) at System.Data.Services.Client.ResourceBinder.VisitMethodCall(MethodCallExpression mce) at System.Data.Services.Client.ALinqExpressionVisitor.Visit(Expression exp) at System.Data.Services.Client.DataServiceALinqExpressionVisitor.Visit(Expression exp) at System.Data.Services.Client.ALinqExpressionVisitor.VisitExpressionList(ReadOnlyCollection1 original)
at System.Data.Services.Client.ALinqExpressionVisitor.VisitMethodCall(MethodCallExpression m)
at System.Data.Services.Client.ResourceBinder.VisitMethodCall(MethodCallExpression mce)
at System.Data.Services.Client.ALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.DataServiceALinqExpressionVisitor.Visit(Expression exp)
at System.Data.Services.Client.ResourceBinder.Bind(Expression e)
at System.Data.Services.Client.DataServiceQueryProvider.Translate(Expression e)
at System.Data.Services.Client.DataServiceQuery1.Execute() at System.Data.Services.Client.DataServiceQuery1.GetEnumerator()
at System.Data.Services.Client.DataServiceQuery`1.System.Collections.IEnumerable.GetEnumerator()

I tried to follow the suggestions at this question but all I got is one of the above two errors.

任何关于如何开展这一简单行动的想法?

Answer 1

You are wanting to make a decision (in this case "order"), based on an aggregate operation (count).
That kind of aggregate operation is not supported in OData queries (for now?).

See this this question for more information: Collection Exists Criteria in WCF Data Services

In the end, you would have to deal with filtering/ordering the data in a different way. At least 2 possible solutions:

Pull more data down to the client, and filter it there.
If you control the server, then you can expose a specialized service operation to return the result (obviously not the case when Netflix is your data source)

友情链接