一、在.Net Core中使用Ef的聚合函数报错: 类似函数: 1,使用FirstOrDefault() 来代替 First() 2、使用SingleOrDefault 来代替 Single 3、使用 ElementAtOrDefault 来代替 .ElementAt 4、如果是在Average, Sum等中报错 错误如下: Sequence contains no elements 二、在.Net Core的 内存列表 Linq 聚合函数解决方案 v...
一、在.Net Core中使用Ef的聚合函数报错: 类似函数: 1,使用FirstOrDefault() 来代替 First() 2、使用SingleOrDefault 来代替 Single 3、使用 ElementAtOrDefault 来代替 .ElementAt 4、如果是在Average, Sum等中报错 错误如下: Sequence contains no elements 二、在.Net Core的 内存列表 Linq 聚合函数解决方案 v...
var value = context.Products.Where(t => t.CategoryId == catId).Select(t => t.Version).DefaultIfEmpty().Max(); throwsSystem.InvalidOperationException: Sequence contains no elements. at int lambda_method(Closure, QueryContext, DbDataReader, ResultContext, int[], ResultCoordinator) at bool Micr...
CommandType='Text',CommandTimeout='30']SELECTMAX([s].[Id])FROM[Sys_User]AS[s]WHERE[s].[Id]<0Unhandled exception.System.InvalidOperationException:Sequence contains noelements.atlambda_method7(Closure,QueryContext,DbDataReader,
SELECT MAX([s].[Id]) FROM [Sys_User] AS [s] WHERE [s].[Id] < 0 Unhandled exception. System.InvalidOperationException: Sequence contains no elements. at lambda_method7(Closure , QueryContext , DbDataReader , ResultContext , SingleQueryResultCoordinator ) ...
MaxOrDefault :原函数 Max 的不抛异常版本,异常返回默认值; AverageOrDefault :原函数 Average 的不抛异常版本,异常返回默认值。 (在线示例:MinOrDefault | C# Online Compiler) // throw 'Sequence contains no elements' newint[0].Min; newint[0].MinOrDefault;// 0 ...
Queries that project elements out of the JSON document into results Updating and saving changes to JSON documentsThe existing documentation from What's New in EF7 provides detailed information on JSON mapping, queries, and updates. This documentation now also applies to SQLite.Tip...
A model finalizing convention will typically iterate over the entire model configuring model elements as it goes. So, in this case, we will find every discriminator in the model and configure it:C# Copy public class DiscriminatorLengthConvention2 : IModelFinalizingConvention { public void Process...
Documentation (zero or one) Annotation elements (zero or more)Applicable AttributesThe table below describes the attributes that can be applied to the Parameter element.Expand table Attribute NameIs RequiredValue Name Yes The name of the parameter. Type Yes The parameter type. Mode No In, Out,...
//根据表达式解析的方法结果,直接找到对应的处理引擎,这里我们挑一个,max为例子,看看它是怎么处理的 varqueryMethodName = mergeQueryCompilerContext.GetQueryMethodName; switch(queryMethodName) { casenameof(Enumerable.First): return EnsureResultTypeMergeExecute<TResult>(typeof(FirstSkipAsyncInMemoryMergeEngine<...