使用自定义ValueConverter时Select上的System.InvalidCastException

Question

问题

我正在尝试在我的一个实体中引入强类型ID。 为此，我遵循了https://andrewlock.net/using-strongly-typed-entity-ids-to-avoid-primitive-obsession-part-3/上的说明

与上述说明的唯一区别是，我试图将ID保留为字符串而不是Guid。

说明的简短摘要（可在此处下载完整示例： https : //drive.google.com/file/d/1_mtYp1c8W6qJoEAY-8NPNjYvsSAif4mz/view?usp=sharing ）：

• 创建具有属性“ Value”的结构“ OrderId”，该结构返回ID的字符串表示形式
• 为Order实体创建类，并添加类型为“ OrderId”的属性“ ID”
• 使用DbSet创建DbContext
• 创建一个自定义ValueConverter，将OrderId转换为字符串，反之亦然
• 将值转换器应用于Order实体的Id列
• 为了避免客户端评估，将一个从OrderId到字符串的显式转换运算符添加到OrderId中

使用此设置，将条目添加到“订单”表中没问题。 但是：当我尝试阅读它们时，会引发以下异常：

System.InvalidCastException
  HResult=0x80004002
  Message=Invalid cast from 'System.String' to 'StronglyTypedIds.OrderId'.
  Source=System.Private.CoreLib
  StackTrace:
   at System.Convert.DefaultToType(IConvertible value, Type targetType, IFormatProvider provider) in E:\A\_work\644\s\src\mscorlib\shared\System\Convert.cs:line 309
   at Microsoft.EntityFrameworkCore.Storage.ValueConversion.ValueConverter`2.Sanitize[T](Object value) in /_/src/EFCore/Storage/ValueConversion/ValueConverter`.cs:line 52
   at Microsoft.EntityFrameworkCore.Storage.ValueConversion.ValueConverter`2.<>c__DisplayClass3_0`2.<SanitizeConverter>b__0(Object v) in /_/src/EFCore/Storage/ValueConversion/ValueConverter`.cs:line 43
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMapping.CreateParameter(DbCommand command, String name, Object value, Nullable`1 nullable) in /_/src/EFCore.Relational/Storage/RelationalTypeMapping.cs:line 515
   at Microsoft.EntityFrameworkCore.Storage.Internal.TypeMappedRelationalParameter.AddDbParameter(DbCommand command, Object value) in /_/src/EFCore.Relational/Storage/Internal/TypeMappedRelationalParameter.cs:line 66
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalParameterBase.AddDbParameter(DbCommand command, IReadOnlyDictionary`2 parameterValues) in /_/src/EFCore.Relational/Storage/Internal/RelationalParameterBase.cs:line 45
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.CreateCommand(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues) in /_/src/EFCore.Relational/Storage/Internal/RelationalCommand.cs:line 375
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.Execute(IRelationalConnection connection, DbCommandMethod executeMethod, IReadOnlyDictionary`2 parameterValues) in /_/src/EFCore.Relational/Storage/Internal/RelationalCommand.cs:line 149
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.ExecuteReader(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues) in /_/src/EFCore.Relational/Storage/Internal/RelationalCommand.cs:line 119
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.Enumerator.BufferlessMoveNext(DbContext _, Boolean buffer) in /_/src/EFCore.Relational/Query/Internal/QueryingEnumerable.cs:line 111
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.Enumerator.MoveNext() in /_/src/EFCore.Relational/Query/Internal/QueryingEnumerable.cs:line 93
   at System.Linq.Enumerable.TryGetFirst[TSource](IEnumerable`1 source, Boolean& found) in E:\A\_work\286\s\corefx\src\System.Linq\src\System\Linq\First.cs:line 63
   at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.ResultEnumerable`1.GetEnumerator() in /_/src/EFCore/Query/Internal/LinqOperatorProvider.cs:line 294
   at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.<_TrackEntities>d__17`2.MoveNext() in /_/src/EFCore/Query/Internal/LinqOperatorProvider.cs:line 185
   at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext() in /_/src/EFCore/Query/Internal/LinqOperatorProvider.cs:line 143
   at System.Linq.Enumerable.TryGetFirst[TSource](IEnumerable`1 source, Boolean& found) in E:\A\_work\286\s\corefx\src\System.Linq\src\System\Linq\First.cs:line 63
   at System.Linq.Enumerable.First[TSource](IEnumerable`1 source) in E:\A\_work\286\s\corefx\src\System.Linq\src\System\Linq\First.cs:line 14
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass15_1`1.<CompileQueryCore>b__0(QueryContext qc) in /_/src/EFCore/Query/Internal/QueryCompiler.cs:line 132
   at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source, Expression`1 predicate) in E:\A\_work\286\s\corefx\src\System.Linq.Queryable\src\System\Linq\Queryable.cs:line 741
   at StronglyTypedIds.Program.Main() in <path_to_project>\StronglyTypedIds\StronglyTypedIds\Program.cs:line 29

奇怪的是，这似乎取决于我如何构建Where-query：

var order = dbContext.Orders.Where(o => (string)o.Id == "1").ToList();                             // works


const string idAsStringConstant = "1";
order = dbContext.Orders.Where(o => (string)o.Id == idAsStringConstant).ToList();                  // works


var idAsStringVariable = "1";
order = dbContext.Orders.Where(o => (string)o.Id == idAsStringVariable).ToList();                  // doesn't work


order = dbContext.Orders.Where(o => (string)o.Id == OrderId.Parse("1").StringValue).ToList();      // doesn't work

重现步骤

这是一个带有示例的VS2019小型解决方案： https ://drive.google.com/file/d/1_mtYp1c8W6qJoEAY-8NPNjYvsSAif4mz/view?usp=sharing

更多技术细节

EF Core版本：2.2.6数据库提供程序：Microsoft.EntityFrameworkCore.SqlServer和Microsoft.EntityFrameworkCore.Sqlite操作系统：Windows 10 1809 IDE：（例如Visual Studio 2019 16.1.6）

Answer 1

好的，这是实体框架中的错误。 如果我安装了.NET Core和Entity Framework Core 3.0版的预览版，则它将按预期工作。 此外，似乎还有一个针对2.2版的修复程序，该修复程序尚未发布（请参阅https://github.com/aspnet/EntityFrameworkCore/issues/17610 ）。