通用Linq查询NotSupportedException:无法解析表达式 [英] Generic Linq query NotSupportedException: Could not parse expression
问题描述
我正在尝试通过辅助类来过滤Entity Framework核心中的某些结果，但出现此错误，我不知道为什么:
I'm trying to filter some results in Entity Framework core generically through a helper class but I'm getting this error and I don't know why:
NotSupportedException: Could not parse expression 'value(Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable'1[eVendCustomerDAL.DomainModels.Bin]).Any(__funcTest_0)': The given arguments did not match the expected arguments: Object of type 'System.Linq.Expressions.TypedParameterExpression' cannot be converted to type 'System.Linq.Expressions.LambdaExpression'.
这是发生错误的地方:
public virtual Revision<DTO> GetStateAsRevision(
Expression<Func<Domain, bool>> query) {
//get all the stateful data from the database
DbSet<Domain> oriSet = db.Set<Domain>();
//query all the data
List<Domain> oriList = oriSet.Where(query).ToList();
该错误似乎是由于我要推送的query参数而发生的，并且仅在运行时发生.我不确定是否应该归咎于它的通用性.泛型是类，而不是接口.
The error seems to occur because of the query parameter that I'm pushing through and it only occurs as runtime. I'm not sure if the fact it's generic is to blame. The generics are classes and not interfaces also.
where DTO : BaseRevisionDTO
where Domain : BaseTrackedObject
where DomainRevision : BaseRevision
然后我使用以下代码段构建表达式:
I then build the expression using the following snippets:
private Expression<Func<Domain, bool>> GetDomainSearchExpression(Func<Domain, bool> shortFunction) {
DbSet<Domain> modelTable = CustomerContext.Set<Domain>();
Expression<Func<Domain, bool>> expr =
d =>
modelTable.Any(shortFunction);
return expr;
}
protected override Func<DomainModels.Bin, bool> GetDomainSearchFunction() {
return x => x.Station.Machine.UniqueId == MachineID;
}
所以，如果我像上面这样调用上面的代码:
So if I call the above code like so:
GetStateAsRevision(GetDomainSearchExpression(GetDomainSearchFunction()));
它将在以下位置出现错误:
It will error at:
List<Domain> oriList = oriSet.Where(query).ToList();
这是整个堆栈跟踪:
NotSupportedException: Could not parse expression 'value(Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1[eVendCustomerDAL.DomainModels.Bin]).Any(__shortFunction_0)': The given arguments did not match the expected arguments: Object of type 'System.Linq.Expressions.TypedParameterExpression' cannot be converted to type 'System.Linq.Expressions.LambdaExpression'.
Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.CreateExpressionNode(Type nodeType, MethodCallExpressionParseInfo parseInfo, Object[] additionalConstructorParameters)
Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.Parse(string associatedIdentifier, IExpressionNode source, IEnumerable<Expression> arguments, MethodCallExpression expressionToParse)
Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression(MethodCallExpression methodCallExpression, string associatedIdentifier)
Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseTree(Expression expressionTree)
Remotion.Linq.Parsing.Structure.QueryParser.GetParsedQuery(Expression expressionTreeRoot)
Remotion.Linq.Parsing.ExpressionVisitors.SubQueryFindingExpressionVisitor.Visit(Expression expression)
System.Linq.Expressions.ExpressionVisitor.VisitLambda<T>(Expression<T> node)
System.Linq.Expressions.Expression.Accept(ExpressionVisitor visitor)
Remotion.Linq.Parsing.ExpressionVisitors.SubQueryFindingExpressionVisitor.Visit(Expression expression)
System.Linq.Enumerable+SelectListPartitionIterator.ToArray()
System.Linq.Enumerable.ToArray<TSource>(IEnumerable<TSource> source)
Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.Parse(string associatedIdentifier, IExpressionNode source, IEnumerable<Expression> arguments, MethodCallExpression expressionToParse)
Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression(MethodCallExpression methodCallExpression, string associatedIdentifier)
Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseTree(Expression expressionTree)
Remotion.Linq.Parsing.Structure.QueryParser.GetParsedQuery(Expression expressionTreeRoot)
Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore<TResult>(Expression query, INodeTypeProvider nodeTypeProvider, IDatabase database, ILogger logger, Type contextType)
Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler+<>c__DisplayClass19_0.<CompileQuery>b__0()
Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore<TFunc>(object cacheKey, Func<Func<QueryContext, TFunc>> compiler)
Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute<TResult>(Expression query)
Remotion.Linq.QueryableBase.GetEnumerator()
System.Collections.Generic.List..ctor(IEnumerable<T> collection)
System.Linq.Enumerable.ToList<TSource>(IEnumerable<TSource> source)
eVendWebAPI.Helpers.DALHelpers.GetRevisionHelper.GetStateAsRevision(Expression<Func<DomainModel, bool>> query) in GetRevisionHelper.cs
+
List<DomainModel> oriList = oriSet.Where(query).ToList();
eVendWebAPI.Helpers.DALHelpers.GetRevisionHelper.GetRevision(Expression<Func<DomainModel, bool>> query) in GetRevisionHelper.cs
+
return GetStateAsRevision(query);
eVendWebAPI.Areas.Customer.Controllers.Base.BaseAPIRevisionController.Get() in BaseAPIRevisionController.cs
+
return Ok(helper.GetRevision(searchExpr));
lambda_method(Closure , object , Object[] )
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeActionMethodAsync>d__27.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeNextActionFilterAsync>d__25.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeNextResourceFilter>d__22.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ResourceExecutedContext context)
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeAsync>d__20.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
Microsoft.AspNetCore.Builder.RouterMiddleware+<Invoke>d__4.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
Microsoft.AspNetCore.Builder.RouterMiddleware+<Invoke>d__4.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware+<Invoke>d__18.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware+<Invoke>d__18.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
Microsoft.VisualStudio.Web.BrowserLink.BrowserLinkMiddleware+<ExecuteWithFilter>d__7.MoveNext()
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware+<Invoke>d__7.MoveNext()
推荐答案
您的shortFunction是Func<>而不是Expression，因此无法将其转换为SQL.尝试改为输入Expression<Func<>>.
Your shortFunction is a Func<> and not an Expression so it can't be converted to SQL. Try making it's type Expression<Func<>> instead.
C#编译器具有特殊的逻辑，可将lambda转换为两种类型-如果所需的结果类型为Func<>，则它将其转换为编译后的代码，如果结果类型为Expression，则将其转换为Expression代表代码的树(为LINQ添加的秘籍).数据提供者可以读取该表达式树并为所涉及的数据库发出代码(例如SQL)，但不能将已编译的IL代码反编译回可以用另一种语言输出的内容.
The C# compiler has special logic to convert a lambda into two types - if the desired result type is Func<> then it converts it to compiled code and if the result type if Expression it converts it to an Expression tree that represents the code (a cheat added for LINQ). A data provider can read that expression tree and emit code for the database in question (such as SQL) but it can't decompile the compiled IL code back into something it can output in another language.
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