[英]LINQ: Translating a SQL WITH clause to LINQ and Entity Framework
[英]Translating Entity Framework Model to Dto in Linq
我在使用以下代碼將Entity Framework 6模型轉換為Dto時遇到問題。 在閱讀Sacha Barber的CodeProject文章之后,我多次使用這種將Entities轉換為Dtos的方法。 該代碼昨晚正在運行,因此今天早上對模型的更改可能影響了該代碼。
只是要注意, layoutTransator
對象已從Unity IoC容器正確加載。
我已經審查了這個Stackoverflow問題,但它並沒有真正涵蓋我的問題。
實體模型
加載實體框架模型
private readonly PortalEntities ctx;
private readonly IEntityDtoTranlator<Layout, LayoutsDto> layoutTranslator;
[InjectionConstructor]
public Dal(IContextFactory<JcbManufacturingPortalEntities> factory,
IEntityDtoTranlator<Layout, LayoutsDto> layoutTransator))
{
ctx = factory.Create(ConfigurationManager.ConnectionStrings[EntityConnection].ConnectionString, EntityPassword);
this.layoutTranslator = layoutTransator;
}
public List<LayoutsDto> GetDiplayLayouts(string machineAssetName)
{
try
{
return (ctx.Layouts.Where(m => m.Hardware.AssetName.Equals(machineAssetName))
.Select(l => layoutTranslator.TranslatetoDto(l))).ToList();
}
catch (Exception ex)
{
throw;
}
}
如果我按以下方式分解加載代碼,則它可以正常工作。 Linq調用該方法必定是一個問題。
List<Layout> layout = (ctx.Layouts.Where(m => m.Hardware.AssetName.Equals(machineAssetName))).ToList();
LayoutsDto dto = layoutTranslator.TranslatetoDto(layout.First());
Dto
public class LayoutsDto
{
[Key]
public int ID { get; set; }
[DefaultValue(0)]
[Range(0,3600000)]
public int Duration { get; set; }
[DefaultValue(0)]
public bool OutOfShift { get; set; }
public byte FlipOrder { get; set; }
public List<ScreenDto> Screens { get; set; }
}
轉換器
internal class LayoutTranslator<TEntity, TDto> : IEntityDtoTranlator<Layout, LayoutsDto>
{
public LayoutsDto TranslatetoDto(Layout entity)
{
return new LayoutsDto
{
Duration = entity.DisplayDuration,
FlipOrder = entity.FlipOrder,
ID = entity.ID,
OutOfShift = entity.IsOutOfShiftScreen
};
}
public Layout TranslateToEntity(LayoutsDto dto)
{
return new Layout
{
DisplayDuration = dto.Duration,
FlipOrder = dto.FlipOrder,
ID = dto.ID,
IsOutOfShiftScreen = dto.OutOfShift
};
}
}
例外
一點是, TranslatetoDto(Jmp.Andon.Service.Data.Layout)
方法不在Jmp.Andon.Models.LayoutsDto
對象中
LINQ to Entities does not recognize the method 'Jmp.Andon.Models.LayoutsDto TranslatetoDto(Jmp.Andon.Service.Data.Layout)' method, and this method cannot be translated into a store expression.
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.DefaultTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator`1.Translate(ExpressionConverter parent, Expression linq)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq)
at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert()
at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClassb.<GetResults>b__a()
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClassb.<GetResults>b__9()
at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at System.Lazy`1.get_Value()
at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Jmp.Andon.Service.Data.Dal.GetDiplayLayouts(String machineAssetName) in c:\Perforce\Development\JMP v2\Jmp.Display\Jmp.Display.Service\Data\Dal.cs:line 38
您只需要更改在其中調用TranslateDto
方法的上下文。 目前,您正在告訴L2E該方法將在DB端運行,但是您的方法無法轉換為SQL,因此無法以這種方式執行。
您需要強制查詢在客戶端上執行該方法,然后將查詢從L2E切換到LINQ To Objects,即
return (ctx.Layouts.Where(m => m.Hardware.AssetName.Equals(machineAssetName))
.AsEnumerable() // <-- Here's the switch
.Select(l => layoutTranslator.TranslatetoDto(l)));
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