我正在尝试连接一些基于IQueryable接口的框架(即OData,如果您想知道的话)。
可以使用以下代码段描述我当前的问题:
var queryable = database.GetCollection<MyItems>("myItems").AsQueryable();
var count1 = queryable.Select(x => x.Order.StateInfo).Count();
// var count2 = queryable.Select(x => x.Order).Select(x => x.StateInfo).Count();
此代码有效,但是如果您取消注释最后一行,则会得到:
System.ArgumentException: Expression of type 'System.Collections.Generic.IEnumerable`1[MyApp.Common.Models.StateInfo]'
cannot be used for parameter of type 'System.Linq.IQueryable`1[MyApp.Common.Models.StateInfo]' of method
'Int32 Count[StateInfo](System.Linq.IQueryable`1[MyApp.Common.Models.StateInfo])' (Parameter 'arg0')
at System.Dynamic.Utils.ExpressionUtils.ValidateOneArgument(MethodBase method, ExpressionType nodeKind, Expression arguments, ParameterInfo pi, String methodParamName, String argumentParamName, Int32 index)
at System.Linq.Expressions.Expression.Call(MethodInfo method, Expression arg0)
at System.Linq.Expressions.MethodCallExpression1.Rewrite(Expression instance, IReadOnlyList`1 args)
at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
at MongoDB.Driver.Linq.Processors.Transformer.Visit(Expression node)
at MongoDB.Driver.Linq.Processors.Transformer.Transform(Expression node)
at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.Prepare(Expression expression)
at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.Translate(Expression expression)
at MongoDB.Driver.Linq.MongoQueryProviderImpl`1.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
at MongoDB.Driver.Linq.MongoQueryable.CountAsync[TSource](IMongoQueryable`1 source, CancellationToken cancellationToken)
似乎驱动程序尝试在内存中执行某些操作,从而丢弃了整个IQueryable
,因此所有后续调用均失败(例如Select / Where / ...)。带有两个后续Select
或Select/Where
对的查询会被中毒,无法在任何地方使用。例如:
var queryable = database.GetCollection<MyItems>("myItems").AsQueryable();
var count1 = queryable.Select(x => x.Order).Where(x => x.StateInfo != null).Count();
// System.InvalidOperationException: '{document}.StateInfo is not supported.'
我该怎么办?也许我可以在某个地方举报?