这是一个关于 InvalidOperationException 的问题,消息类成员X未映射。
我们的一个系统对于每个具有框架版本3.5的LinqToSql实体都具有相同的基本实体。
我遇到了一个非常奇怪的问题,我开始研究它。我做了一个非常小的项目,以便能够更轻松地本地化问题。
实体基类
public abstract class EntityBase
{
public virtual long ID { get; set; }
}
DataContext和实体
[Database(Name = "TestDatabase")]
public class EntitiesDataContext : DataContext
{
public EntitiesDataContext() :
base(Settings.Default.TestDatabaseConnectionString, new AttributeMappingSource())
{
}
}
[Table(Name = "dbo.MyEntity")]
public class MyEntity : EntityBase
{
private long _EntityID;
[Column(Name = "EntityID", Storage = "_EntityID")]
public override long ID
{
get { return _EntityID; }
set { _EntityID = value; }
}
[Column] public string Title;
}
问题是覆盖 ID 。我使用不同的映射属性/属性名称设置做了很多变化,但似乎问题不是命名而是基类。 .NET3.5和.NET4.0之间也存在差异。
因此,对于以下陈述,想象一下
using (var ctx = new EntitiesDataContext())
{
//statement
}
周围。
GetTable()是GetTable<MyEntity>().
失败表示类成员EntityBase.ID未映射。异常。 作品表示预期的行为。
1(3.5)工作:
var result = ctx.GetTable().Where(i => i.ID == 2).FirstOrDefault();
2(3.5)失败:
var result = ctx.GetTable().FirstOrDefault(i => i.ID == 2);
3(3.5)工作:
var result = ctx.GetTable().FirstOrDefault(i => i.ID.Equals(2));
4(3.5)工作:
var result = ctx.GetTable().Where(i => true).FirstOrDefault(i => i.ID == 2);
5(3.5)工作:
var result = ctx.GetTable().Where(i => i.ID == 2).FirstOrDefault();
6(4.0)失败:
var result = ctx.GetTable().Where(i => i.ID == 2).FirstOrDefault()
7(4.0)工作:
var result = ctx.GetTable().Where(i => i.ID.Equals(2)).FirstOrDefault();
8(4.0) FAILS (多余6)
var result = ctx.GetTable().FirstOrDefault(i => i.ID == 2);
9(4.0)工作:
var result = ctx.GetTable().FirstOrDefault(i => i.ID.Equals(2));
10(4.0)工作:
ctx.GetTable().Where(i => true).FirstOrDefault(i => i.ID == 2);
因此 我无法弄清楚它失败的原因。特别是,为什么这样做
var result = ctx.GetTable().Where(i => true).FirstOrDefault(i => i.ID == 2);
如果带有谓词的FirstOrDefault没有?为什么Equals适用于==不是。
我正在寻找一些Equals和==差异描述,但它没有给我Where(i =&gt; true)...的答案。
似乎不是关于查询而是对象初始化。这是因为:
在4.0工作中:
var result = ctx.GetTable().Where(i => i.ID == 2).Select(i => i.Title).FirstOrDefault();
但是:)
在4.0中也是如此:
var result = ctx.GetTable().FirstOrDefault();
所以可能不是对象初始化?
由LinqToSql构建的SQL是==和Equals的相同。
的相同Where(i => true).FirstOrDefault(i => i.ID == 2)
和
FirstOrDefault(i => i.ID == 2)
在FirstOrDefault之前没有SQL查询,它正如预期的那样正确构建查询。 Where(i =&gt; true)只是继续SQL查询中包含的表达式构建和FirstOrDefault谓词。
有什么猜测? :)
谢谢
#### Continuation(在.NET4.0中)
我设置了5种简单的方法来轻松检入反射器:
public void WithEquals(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().FirstOrDefault(i => i.ID.Equals(2));
}
public void WithFakeWhereAndOperator(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().Where(i => true).FirstOrDefault(i => i.ID == 2);
}
public void WithOperator(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().FirstOrDefault(i => i.ID == 2);
}
public void WithOperatorSelect(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().Where(i => i.ID == 2).Select(i => i).FirstOrDefault();
}
public void WithOperatorAndWhere(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().Where(i => i.ID == 2).FirstOrDefault();
}
WithOperator和WithOperatorAndWhere失败,但这里是 MSIL 以及我看到的内容:
WithOperator
.method public hidebysig instance void WithOperator(class LinqToSqlTest.EntitiesDataContext ctx) cil managed
{
.maxstack 5
.locals init (
[0] class [System.Core]System.Linq.Expressions.ParameterExpression CS$0$0000,
[1] class [System.Core]System.Linq.Expressions.ParameterExpression[] CS$0$0001)
L_0000: nop
L_0001: ldarg.1
L_0002: callvirt instance class [System.Data.Linq]System.Data.Linq.Table`1<!!0> [System.Data.Linq]System.Data.Linq.DataContext::GetTable<class LinqToSqlTest.MyEntity>()
L_0007: ldtoken LinqToSqlTest.MyEntity
L_000c: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0011: ldstr "i"
L_0016: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_001b: stloc.0
L_001c: ldloc.0
L_001d: ldtoken instance int64 LinqToSqlTest.EntityBase::get_ID()
L_0022: call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle(valuetype [mscorlib]System.RuntimeMethodHandle)
L_0027: castclass [mscorlib]System.Reflection.MethodInfo
L_002c: call class [System.Core]System.Linq.Expressions.MemberExpression [System.Core]System.Linq.Expressions.Expression::Property(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo)
L_0031: ldc.i4.2
L_0032: conv.i8
L_0033: box int64
L_0038: ldtoken int64
L_003d: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0042: call class [System.Core]System.Linq.Expressions.ConstantExpression [System.Core]System.Linq.Expressions.Expression::Constant(object, class [mscorlib]System.Type)
L_0047: call class [System.Core]System.Linq.Expressions.BinaryExpression [System.Core]System.Linq.Expressions.Expression::Equal(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.Expression)
L_004c: ldc.i4.1
L_004d: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_0052: stloc.1
L_0053: ldloc.1
L_0054: ldc.i4.0
L_0055: ldloc.0
L_0056: stelem.ref
L_0057: ldloc.1
L_0058: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, bool>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_005d: call !!0 [System.Core]System.Linq.Queryable::FirstOrDefault<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, bool>>)
L_0062: pop
L_0063: ret
}
WithFakeWhereAndOperator
.method public hidebysig instance void WithFakeWhereAndOperator(class LinqToSqlTest.EntitiesDataContext ctx) cil managed
{
.maxstack 5
.locals init (
[0] class [System.Core]System.Linq.Expressions.ParameterExpression CS$0$0000,
[1] class [System.Core]System.Linq.Expressions.ParameterExpression[] CS$0$0001)
L_0000: nop
L_0001: ldarg.1
L_0002: callvirt instance class [System.Data.Linq]System.Data.Linq.Table`1<!!0> [System.Data.Linq]System.Data.Linq.DataContext::GetTable<class LinqToSqlTest.MyEntity>()
L_0007: ldtoken LinqToSqlTest.MyEntity
L_000c: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0011: ldstr "i"
L_0016: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_001b: stloc.0
L_001c: ldc.i4.1
L_001d: box bool
L_0022: ldtoken bool
L_0027: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_002c: call class [System.Core]System.Linq.Expressions.ConstantExpression [System.Core]System.Linq.Expressions.Expression::Constant(object, class [mscorlib]System.Type)
L_0031: ldc.i4.1
L_0032: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_0037: stloc.1
L_0038: ldloc.1
L_0039: ldc.i4.0
L_003a: ldloc.0
L_003b: stelem.ref
L_003c: ldloc.1
L_003d: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, bool>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_0042: call class [System.Core]System.Linq.IQueryable`1<!!0> [System.Core]System.Linq.Queryable::Where<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, bool>>)
L_0047: ldtoken LinqToSqlTest.MyEntity
L_004c: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0051: ldstr "i"
L_0056: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_005b: stloc.0
L_005c: ldloc.0
L_005d: ldtoken instance int64 LinqToSqlTest.EntityBase::get_ID()
L_0062: call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle(valuetype [mscorlib]System.RuntimeMethodHandle)
L_0067: castclass [mscorlib]System.Reflection.MethodInfo
L_006c: call class [System.Core]System.Linq.Expressions.MemberExpression [System.Core]System.Linq.Expressions.Expression::Property(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo)
L_0071: ldc.i4.2
L_0072: conv.i8
L_0073: box int64
L_0078: ldtoken int64
L_007d: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0082: call class [System.Core]System.Linq.Expressions.ConstantExpression [System.Core]System.Linq.Expressions.Expression::Constant(object, class [mscorlib]System.Type)
L_0087: call class [System.Core]System.Linq.Expressions.BinaryExpression [System.Core]System.Linq.Expressions.Expression::Equal(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.Expression)
L_008c: ldc.i4.1
L_008d: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_0092: stloc.1
L_0093: ldloc.1
L_0094: ldc.i4.0
L_0095: ldloc.0
L_0096: stelem.ref
L_0097: ldloc.1
L_0098: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, bool>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_009d: call !!0 [System.Core]System.Linq.Queryable::FirstOrDefault<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, bool>>)
L_00a2: pop
L_00a3: ret
}
如我所见, FirstOrDefault 调用之间没有区别, WithFakeWhereAndOperator 仅包含'关于Where语句的几行:
WithEquals
.method public hidebysig instance void WithEquals(class LinqToSqlTest.EntitiesDataContext ctx) cil managed
{
.maxstack 7
.locals init (
[0] class [System.Core]System.Linq.Expressions.ParameterExpression CS$0$0000,
[1] class [System.Core]System.Linq.Expressions.Expression[] CS$0$0001,
[2] class [System.Core]System.Linq.Expressions.ParameterExpression[] CS$0$0002)
L_0000: nop
L_0001: ldarg.1
L_0002: callvirt instance class [System.Data.Linq]System.Data.Linq.Table`1<!!0> [System.Data.Linq]System.Data.Linq.DataContext::GetTable<class LinqToSqlTest.MyEntity>()
L_0007: ldtoken LinqToSqlTest.MyEntity
L_000c: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0011: ldstr "i"
L_0016: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_001b: stloc.0
L_001c: ldloc.0
L_001d: ldtoken instance int64 LinqToSqlTest.EntityBase::get_ID()
L_0022: call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle(valuetype [mscorlib]System.RuntimeMethodHandle)
L_0027: castclass [mscorlib]System.Reflection.MethodInfo
L_002c: call class [System.Core]System.Linq.Expressions.MemberExpression [System.Core]System.Linq.Expressions.Expression::Property(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo)
L_0031: ldtoken instance bool [mscorlib]System.Int64::Equals(int64)
L_0036: call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle(valuetype [mscorlib]System.RuntimeMethodHandle)
L_003b: castclass [mscorlib]System.Reflection.MethodInfo
L_0040: ldc.i4.1
L_0041: newarr [System.Core]System.Linq.Expressions.Expression
L_0046: stloc.1
L_0047: ldloc.1
L_0048: ldc.i4.0
L_0049: ldc.i4.2
L_004a: conv.i8
L_004b: box int64
L_0050: ldtoken int64
L_0055: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_005a: call class [System.Core]System.Linq.Expressions.ConstantExpression [System.Core]System.Linq.Expressions.Expression::Constant(object, class [mscorlib]System.Type)
L_005f: stelem.ref
L_0060: ldloc.1
L_0061: call class [System.Core]System.Linq.Expressions.MethodCallExpression [System.Core]System.Linq.Expressions.Expression::Call(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo, class [System.Core]System.Linq.Expressions.Expression[])
L_0066: ldc.i4.1
L_0067: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_006c: stloc.2
L_006d: ldloc.2
L_006e: ldc.i4.0
L_006f: ldloc.0
L_0070: stelem.ref
L_0071: ldloc.2
L_0072: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, bool>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_0077: call !!0 [System.Core]System.Linq.Queryable::FirstOrDefault<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, bool>>)
L_007c: pop
L_007d: ret
}
差异更大:
在 WithEquals 中,还有一个额外的
[System.Core]System.Linq.Expressions.Expression[]
初始化,它在方法的中间调用Equals。
另外,我可以看到 WithOperator 使用
call class [System.Core]System.Linq.Expressions.BinaryExpression [System.Core]System.Linq.Expressions.Expression::Equal(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.Expression)
而 WithEquals 使用
call class [System.Core]System.Linq.Expressions.MethodCallExpression [System.Core]System.Linq.Expressions.Expression::Call(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo, class [System.Core]System.Linq.Expressions.Expression[])
这是在第二张图片的第38行。
嗯,也许这是 BinaryExpression 和 MethodCallExpression 之间的区别问题?我将进一步研究这些。
所以
我们有一个工作
public void WithOperatorSelect(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().Where(i => i.ID == 2).Select(i => i).FirstOrDefault();
}
与
相同public void WithOperatorAndWhere(EntitiesDataContext ctx)
{
ctx.GetTable<MyEntity>().Where(i => i.ID == 2).FirstOrDefault();
}
但是有一个额外的假选择有效。
MSIL
WithOperatorAndSelect
.method public hidebysig instance void WithOperatorSelect(class LinqToSqlTest.EntitiesDataContext ctx) cil managed
{
.maxstack 5
.locals init (
[0] class [System.Core]System.Linq.Expressions.ParameterExpression CS$0$0000,
[1] class [System.Core]System.Linq.Expressions.ParameterExpression[] CS$0$0001)
L_0000: nop
L_0001: ldarg.1
L_0002: callvirt instance class [System.Data.Linq]System.Data.Linq.Table`1<!!0> [System.Data.Linq]System.Data.Linq.DataContext::GetTable<class LinqToSqlTest.MyEntity>()
L_0007: ldtoken LinqToSqlTest.MyEntity
L_000c: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0011: ldstr "i"
L_0016: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_001b: stloc.0
L_001c: ldloc.0
L_001d: ldtoken instance int64 LinqToSqlTest.EntityBase::get_ID()
L_0022: call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle(valuetype [mscorlib]System.RuntimeMethodHandle)
L_0027: castclass [mscorlib]System.Reflection.MethodInfo
L_002c: call class [System.Core]System.Linq.Expressions.MemberExpression [System.Core]System.Linq.Expressions.Expression::Property(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo)
L_0031: ldc.i4.2
L_0032: conv.i8
L_0033: box int64
L_0038: ldtoken int64
L_003d: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0042: call class [System.Core]System.Linq.Expressions.ConstantExpression [System.Core]System.Linq.Expressions.Expression::Constant(object, class [mscorlib]System.Type)
L_0047: call class [System.Core]System.Linq.Expressions.BinaryExpression [System.Core]System.Linq.Expressions.Expression::Equal(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.Expression)
L_004c: ldc.i4.1
L_004d: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_0052: stloc.1
L_0053: ldloc.1
L_0054: ldc.i4.0
L_0055: ldloc.0
L_0056: stelem.ref
L_0057: ldloc.1
L_0058: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, bool>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_005d: call class [System.Core]System.Linq.IQueryable`1<!!0> [System.Core]System.Linq.Queryable::Where<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, bool>>)
L_0062: ldtoken LinqToSqlTest.MyEntity
L_0067: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_006c: ldstr "i"
L_0071: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_0076: stloc.0
L_0077: ldloc.0
L_0078: ldc.i4.1
L_0079: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_007e: stloc.1
L_007f: ldloc.1
L_0080: ldc.i4.0
L_0081: ldloc.0
L_0082: stelem.ref
L_0083: ldloc.1
L_0084: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, class LinqToSqlTest.MyEntity>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_0089: call class [System.Core]System.Linq.IQueryable`1<!!1> [System.Core]System.Linq.Queryable::Select<class LinqToSqlTest.MyEntity, class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, !!1>>)
L_008e: call !!0 [System.Core]System.Linq.Queryable::FirstOrDefault<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>)
L_0093: pop
L_0094: ret
}
WithOperatorAndWhere
.method public hidebysig instance void WithOperatorAndWhere(class LinqToSqlTest.EntitiesDataContext ctx) cil managed
{
.maxstack 5
.locals init (
[0] class [System.Core]System.Linq.Expressions.ParameterExpression CS$0$0000,
[1] class [System.Core]System.Linq.Expressions.ParameterExpression[] CS$0$0001)
L_0000: nop
L_0001: ldarg.1
L_0002: callvirt instance class [System.Data.Linq]System.Data.Linq.Table`1<!!0> [System.Data.Linq]System.Data.Linq.DataContext::GetTable<class LinqToSqlTest.MyEntity>()
L_0007: ldtoken LinqToSqlTest.MyEntity
L_000c: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0011: ldstr "i"
L_0016: call class [System.Core]System.Linq.Expressions.ParameterExpression [System.Core]System.Linq.Expressions.Expression::Parameter(class [mscorlib]System.Type, string)
L_001b: stloc.0
L_001c: ldloc.0
L_001d: ldtoken instance int64 LinqToSqlTest.EntityBase::get_ID()
L_0022: call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle(valuetype [mscorlib]System.RuntimeMethodHandle)
L_0027: castclass [mscorlib]System.Reflection.MethodInfo
L_002c: call class [System.Core]System.Linq.Expressions.MemberExpression [System.Core]System.Linq.Expressions.Expression::Property(class [System.Core]System.Linq.Expressions.Expression, class [mscorlib]System.Reflection.MethodInfo)
L_0031: ldc.i4.2
L_0032: conv.i8
L_0033: box int64
L_0038: ldtoken int64
L_003d: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
L_0042: call class [System.Core]System.Linq.Expressions.ConstantExpression [System.Core]System.Linq.Expressions.Expression::Constant(object, class [mscorlib]System.Type)
L_0047: call class [System.Core]System.Linq.Expressions.BinaryExpression [System.Core]System.Linq.Expressions.Expression::Equal(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.Expression)
L_004c: ldc.i4.1
L_004d: newarr [System.Core]System.Linq.Expressions.ParameterExpression
L_0052: stloc.1
L_0053: ldloc.1
L_0054: ldc.i4.0
L_0055: ldloc.0
L_0056: stelem.ref
L_0057: ldloc.1
L_0058: call class [System.Core]System.Linq.Expressions.Expression`1<!!0> [System.Core]System.Linq.Expressions.Expression::Lambda<class [mscorlib]System.Func`2<class LinqToSqlTest.MyEntity, bool>>(class [System.Core]System.Linq.Expressions.Expression, class [System.Core]System.Linq.Expressions.ParameterExpression[])
L_005d: call class [System.Core]System.Linq.IQueryable`1<!!0> [System.Core]System.Linq.Queryable::Where<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>, class [System.Core]System.Linq.Expressions.Expression`1<class [mscorlib]System.Func`2<!!0, bool>>)
L_0062: call !!0 [System.Core]System.Linq.Queryable::FirstOrDefault<class LinqToSqlTest.MyEntity>(class [System.Core]System.Linq.IQueryable`1<!!0>)
L_0067: pop
L_0068: ret
}
差异:
唯一的区别(除了WithOperatorAndSelect有效:))是MSIL中的Select语句。
所以我猜测它不是==运算符/等于问题。但我不知道。
答案 0 :(得分:5)
好吧,这似乎是一个已知的错误:
并且不会修复。
相关问题:
LINQ to SQL - mapping exception when using abstract base classes
LinqToSql and abstract base classes
无论如何,谢谢Frank Tzanabetis的努力。
答案 1 :(得分:2)
我会在黑暗中刺伤。也许它与== staic和.Equals()是虚拟的有关。
因此,你最终会有这样的行为:
object x = 10;
object y = 10;
x == y // returns false as == is static and the compiler statically binds it
// to object, which uses a reference comparison, hence the false
x.Equals(y) // returns true as .Equals is virtual, thus calls the Int32
// implementation of .Equals which does a value type compare.
当你使用“==”时,linqtosql可能无法确定你指的是哪个ID - 它认为它是基类类型,而使用.Equals()它知道你指的是你的具体子类,可以搞清楚。
我不知道,只是一个猜测...