LINQ to Entities无法识别方法'System.String ToString（）'。(LINQ to Entities does not recognize the

LINQ to Entities无法识别方法'System.String ToString（）'。(LINQ to Entities does not recognize the method 'System.String ToString()'. Error happend when trying parse DateTime)

我正在尝试从实体查询中获取自定义数据集，但遗憾的是我收到以下错误：

LINQ to Entities无法识别System.String ToString（）方法的方法，并且此方法无法转换为存储表达式。这是返回数据的自定义类：

public class featuredlist { public string kodg { get; set; } public string excursion { get; set; } public string excursiondate { get; set; } } public IQueryable<featuredlist> GetFeatured(string fdate) { try { var fd = DateTime.Parse(fdate); var uname = HttpContext.Current.User.Identity.Name; var uid = (from x in db.xEmployee where x.Сотрудник.Contains(uname) select x.Kod).FirstOrDefault(); var fl = (from a in db.xGrafik join b in db.xExcursion on a.Excursion equals b.Kod join c in db.xDate on a.КодД equals c.Kod join d in db.xOrder on a.Kod equals d.КодГ where c.Дата == fd & d.Продал == uid orderby c.Дата descending select new featuredlist { kodg = a.Kod.ToString(), excursion = b.Название, //Probably error happend here. excursiondate = (c.Дата) != null ? c.Дата.Value.ToShortDateString : "01.01" }) .AsQueryable(); return fl.Distinct(); } catch (DbEntityValidationException e) { foreach (var eve in e.EntityValidationErrors) { var path = @"d:\error.txt"; using (StreamWriter sw = File.CreateText(path)) { sw.WriteLine("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:", eve.Entry.Entity.GetType().Name, eve.Entry.State); } using (StreamWriter sw1 = File.CreateText(@"d:\error1.txt")) foreach (var ve in eve.ValidationErrors) { sw1.WriteLine("- Property: \"{0}\", Error: \"{1}\"", ve.PropertyName, ve.ErrorMessage); } } throw; } }

异常消息：“LINQ to Entities无法识别方法'System.String ToString（）'方法，并且此方法无法转换为存储表达式。” 堆栈跟踪：“System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.DefaultTranslator.Translate（ExpressionConverter parent，MethodCallExpression call） - System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate（ ExpressionConverter parent，MethodCallExpression linq）System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator 1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator вSystem.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate（ExpressionConverter parent， 1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator вSystem.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator1.Translate（ExpressionConverter parent，表达式linq）System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression（Expression linq）вSystem.Data.Entity.Core.Objects.ELinq.ExpressionC onverter.TranslateLambda（LambdaExpression lambda，DbExpression输入） - System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda（LambdaExpression lambda，DbExpression输入，DbExpressionBinding和绑定），System.Data.Entity.Core.Objects.ELinq.ExpressionConverter .MethodCallTranslator.OneLambdaTranslator.Translate（ExpressionConverter parent，MethodCallExpression call，DbExpression＆source，DbExpressionBinding＆sourceBinding，DbExpression＆lambda）System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate（ExpressionConverter parent，MethodCallExpression call） System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate（ExpressionConverter parent，MethodCallExpression call，SequenceMethod sequenceMethod）System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate（ExpressionConverter parent ，MethodCallExpression linq）вSystem.Da ta.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator 1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator 1.Translate（ExpressionConverter parent，Expression linq）вSystem.Data.Entity.C ore.Objects.ELinq.ExpressionConverter.TranslateExpression（Expression linq）вSystem.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert（）вSystem.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan（Nullable 1 forMergeOption) в System.Data.Entity.Core.Objects.ObjectQuery 1。<> c__DisplayClassb.b__a（）вSystem.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T]（Func 1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) в System.Data.Entity.Core.Objects.ObjectQuery 1。<> c__DisplayClassb.b__9（）вSystem.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult]（Func 1 operation) в System.Data.Entity.Core.Objects.ObjectQuery вSystem.Data 1 operation) в System.Data.Entity.Core.Objects.ObjectQuery 1.GetResults（Nullable 1 forMergeOption) в System.Data.Entity.Core.Objects.ObjectQuery вSystem.Data.Entity.Core.Objects.ObjectQuery1..GetEnumerator> b__0（）вSystem.Lazy1.CreateValue（）вSystem.Lazy1。 LazyInitValue（） 1.get_Value() в System.Data.Entity.Internal.LazyEnumerator вSystem.Data.Entity.Internal.LazyEnumerator1.MoveNext（）ñNe wtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList（JsonWriter writer，IEnumerable values，JsonArrayContract contract，JsonProperty member，JsonContainerContract collectionContract，JsonProperty containerProperty）•Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue（JsonWriter writer，Object value，JsonContract valueContract，JsonProperty member），JsonContainerContract containerContract，JsonProperty containerProperty）Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize（JsonWriter jsonWriter，Object value，Type objectType）Newtonsoft.Json.JsonSerializer.SerializeInternal（JsonWriter jsonWriter，Object value，Type objectType）Newtonsoft.Json。 JsonSerializer.Serialize（JsonWriter jsonWriter，Object value）•System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream（Type type，Object value，Stream writeStream，Encoding effectiveEncoding）System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream（Type type ，对象值，Stream writeStream，Encoding effectiveEncoding）System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream（Type type，Object value，Stream writeStream，HttpContent content）System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync（Type type， Object value，Stream writeStream，HttpContent content，TransportContext transportContext，CancellationToken cancellationToken）---Конецтрассировкастекаизпредыдущегорасположения，гдевозниклоисключение---вSystem.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess（Task task）вSystem.Runtime。 CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification（任务任务） - System.Runtime.CompilerServices.TaskAwaiter.GetResult（），System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext（）“

I'm trying to get custom set of data from entity query, but regratfully I'm getting the following error:

LINQ to Entities does not recognize the method System.String ToString() method, and this method cannot be translated into a store expression. Here is custome class to return data:

public class featuredlist { public string kodg { get; set; } public string excursion { get; set; } public string excursiondate { get; set; } } public IQueryable<featuredlist> GetFeatured(string fdate) { try { var fd = DateTime.Parse(fdate); var uname = HttpContext.Current.User.Identity.Name; var uid = (from x in db.xEmployee where x.Сотрудник.Contains(uname) select x.Kod).FirstOrDefault(); var fl = (from a in db.xGrafik join b in db.xExcursion on a.Excursion equals b.Kod join c in db.xDate on a.КодД equals c.Kod join d in db.xOrder on a.Kod equals d.КодГ where c.Дата == fd & d.Продал == uid orderby c.Дата descending select new featuredlist { kodg = a.Kod.ToString(), excursion = b.Название, //Probably error happend here. excursiondate = (c.Дата) != null ? c.Дата.Value.ToShortDateString : "01.01" }) .AsQueryable(); return fl.Distinct(); } catch (DbEntityValidationException e) { foreach (var eve in e.EntityValidationErrors) { var path = @"d:\error.txt"; using (StreamWriter sw = File.CreateText(path)) { sw.WriteLine("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:", eve.Entry.Entity.GetType().Name, eve.Entry.State); } using (StreamWriter sw1 = File.CreateText(@"d:\error1.txt")) foreach (var ve in eve.ValidationErrors) { sw1.WriteLine("- Property: \"{0}\", Error: \"{1}\"", ve.PropertyName, ve.ErrorMessage); } } throw; } }

Exception message: "LINQ to Entities does not recognize the method 'System.String ToString()' method, and this method cannot be translated into a store expression." Stack trace: " в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.DefaultTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MemberInitTranslator.TypedTranslate(ExpressionConverter parent, MemberInitExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateLambda(LambdaExpression lambda, DbExpression input, DbExpressionBinding& binding) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.OneLambdaTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, DbExpression& source, DbExpressionBinding& sourceBinding, DbExpression& lambda) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SelectTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateSet(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.UnarySequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.SequenceMethodTranslator.Translate(ExpressionConverter parent, MethodCallExpression call, SequenceMethod sequenceMethod) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.MethodCallTranslator.TypedTranslate(ExpressionConverter parent, MethodCallExpression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TypedTranslator1.Translate(ExpressionConverter parent, Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.TranslateExpression(Expression linq) в System.Data.Entity.Core.Objects.ELinq.ExpressionConverter.Convert() в System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable1 forMergeOption) в System.Data.Entity.Core.Objects.ObjectQuery1.<>c__DisplayClassb.b__a() в System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess) в System.Data.Entity.Core.Objects.ObjectQuery1.<>c__DisplayClassb.b__9() в System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func1 operation) в System.Data.Entity.Core.Objects.ObjectQuery1.GetResults(Nullable1 forMergeOption) в System.Data.Entity.Core.Objects.ObjectQuery1..GetEnumerator>b__0() в System.Lazy1.CreateValue() в System.Lazy1.LazyInitValue() в System.Lazy1.get_Value() в System.Data.Entity.Internal.LazyEnumerator1.MoveNext() в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty) в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty) в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType) в Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType) в Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value) в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding) в System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding) в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content) в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken) --- Конец трассировка стека из предыдущего расположения, где возникло исключение --- в System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) в System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) в System.Runtime.CompilerServices.TaskAwaiter.GetResult() в System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext()"