Question

我有一个复杂的查询，其中我将从多个公司的表中提取文章，然后按公司ID分组，然后根据lastupdated / published date订购每个组，然后按公司/组排名前2。显然，它是抛出错误，我不想使用asenumerable（），因为它是一个非常大的表，我不希望数据加载到内存中。这是查询：

var articles = (from article in collection.AsQueryable()
                                    where companyIds.Contains(article.CompanyId)
                                    where article.Active
                                    group article by article.CompanyId
                            into companyArticles
                                    select (from a in companyArticles
                                            orderby a.PublicationDate descending
                                            select a).Take((int) maxPerCompany)
                            ).SelectMany(a => a)
                            .OrderByDescending(a => a.PublicationDate)
                            .Skip(checked((int) skip))
                            .Take(checked((int) length))
                            .ToList();

//或linq

var companiesArticles = collection.AsQueryable()
                            .Where(c => companyIds.Contains(c.CompanyId) && c.Active)
                            .GroupBy(a => a.CompanyId, (a, records) =>
                                records.OrderByDescending(a => a.PublicationDate).Take((int) maxPerCompany))
                            .SelectMany(a => a)
                            .OrderByDescending(a => a.PublicationDate)
                            .Skip(checked((int) skip))
                            .Take(checked((int) length))
                            .ToList();

非常感谢任何帮助。

异常消息：表达式树不支持OrderByDescending方法：{document} .OrderByDescending（a =＆gt; a.PublicationDate）。

异常堆栈跟踪：在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall(MethodCallExpression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind（表达式节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindPipeline(Expression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall（MethodCallExpression节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind(Expression node) at MongoDB.Driver.Linq.Processors.EmbeddedPipeline.EmbeddedPipelineBinder.Bind(Expression node, IBindingContext parent) at MongoDB.Driver.Linq.Processors.SerializationBinder.BindEmbeddedPipeline(MethodCallExpression node) at MongoDB.Driver.Linq.Processors.SerializationBinder.VisitMethodCall(MethodCallExpression node) at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor) at MongoDB.Driver.Linq.Processors.SerializationBinder.Visit(Expression node) at MongoDB.Driver.Linq.Processors.Pipeline.MethodCallBinders.SelectBinder.Bind(PipelineExpression pipeline, PipelineBindingContext bindingContext, MethodCallExpression node, IEnumerable 1个参数）在MongoDB.Driver.Linq.Processors.MethodInfoMethodCallBinder 1.Bind(PipelineExpression pipeline, TBindingContext bindingContext, MethodCallExpression node, IEnumerable 1个参数）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall(MethodCallExpression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind（表达式节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindPipeline(Expression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall（MethodCallExpression节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind(Expression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindPipeline（表达式节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall(MethodCallExpression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind（表达式节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindPipeline(Expression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall（MethodCallExpression节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind(Expression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindPipeline（表达式节点）在MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.BindMethodCall(MethodCallExpression node) at MongoDB.Driver.Linq.Processors.PipelineBinderBase 1.Bind（表达式节点）在MongoDB.Driver.Linq.Processors.Pipeline.PipelineBinder.Bind（Expression node，IBsonSerializerRegistry serializerRegistry）在MongoDB.Driver.Linq.MongoQueryProviderImpl 1.Prepare(Expression expression) at MongoDB.Driver.Linq.MongoQueryProviderImpl 1.Translate（表达式表达式）在MongoDB.Driver.Linq.MongoQueryProviderImpl 1.Execute(Expression expression) at MongoDB.Driver.Linq.MongoQueryableImpl 2.GetEnumerator（）在System.Collections.Generic.List 1..ctor(IEnumerable 1个集合）在System.Linq.Enumerable.ToList [TSource]（IEnumerable`1 source）在

不支持MongoDB方法

0 个答案: