有趣的Linq to SQL常见的基类行为

Question

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Entity

[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>().

失败意味着类成员EntityBase.ID未映射.例外.工作意味着预期的行为.

1(3.5)工作:

var result = ctx.GetTable().Where(i => i.ID == 2).FirstOrDefault();

2(在3.5中)失败:

var result = ctx.GetTable().FirstOrDefault(i => i.ID == 2);

3(在3.5中)工作:

var result = ctx.GetTable().FirstOrDefault(i => i.ID.Equals(2));

4(在3.5中)工作:

var result = ctx.GetTable().Where(i => true).FirstOrDefault(i => i.ID == 2);

5(在3.5中)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);

所以 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 => true)......的答案.

It seems that it's not about the query but the object initialization. Because:

in 4.0 WORKS:

var result = ctx.GetTable().Where(i => i.ID == 2).Select(i => i.Title).FirstOrDefault();

but :)

in 4.0 it's also WORKS:

var result = ctx.GetTable().FirstOrDefault();

So maybe not the object initialization?

The SQL being built by LinqToSql is the same for == and Equals. Also the same for

Where(i => true).FirstOrDefault(i => i.ID == 2)

and

FirstOrDefault(i => i.ID == 2)

There is no SQL query until FirstOrDefault, and it builds the query correctly, as it expected. Where(i => true) just continues the expression building and FirstOrDefault predicate included in the SQL queries.

I was looking for other reason in Reflector in MSIL, but found nothing special.

Any guess? :)

Thank you

####Continuation (in .NET4.0)

I set up 5 simple methods to easily check in reflector:

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 and WithOperatorAndWhere fails, but here is the MSIL and what I see:

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 
    }

As I see, there is no difference between the FirstOrDefault calls, the WithFakeWhereAndOperator only 'includes' a few line about the Where statement:

And the 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 
    }

The difference is bigger:

In WithEquals, there is an extra

[System.Core]System.Linq.Expressions.Expression[]

initialization, and it calls Equals in the middle of the method.

Also, I can see that WithOperator uses

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)

while WithEquals uses

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[])

This is in the line 38 on the second image.

Hm, maybe it's a problem about the difference between BinaryExpression and MethodCallExpression? I will make further research about these.

So on

We have a working

public void WithOperatorSelect(EntitiesDataContext ctx)
{
    ctx.GetTable<MyEntity>().Where(i => i.ID == 2).Select(i => i).FirstOrDefault();
}

Same as

public void WithOperatorAndWhere(EntitiesDataContext ctx)
{
    ctx.GetTable<MyEntity>().Where(i => i.ID == 2).FirstOrDefault();
}

but with an extra fake select and it works.

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 
    }

And the difference:

The only difference (in addition to that WithOperatorAndSelect works :) ) is the Select statement in MSIL.

So I guess it's not an == operator/Equals problem. But I don't know.

Answer 1

好吧,这似乎是一个已知的错误:

http://connect.microsoft.com/VisualStudio/feedback/details/394255/linq-to-sql-bug-handling-entities-with-common-base-class

它不会被修复.

相关问题:

LINQ to SQL - 使用抽象基类时的映射异常

LinqToSql和抽象基类

无论如何,谢谢Frank Tzanabetis的努力.