动态+ LINQ编译错误 [英] Dynamic + linq compilation error

问题描述

我会说起来，我正在使用linq对动态数据做一些非常可怕的事情。
但是我不知道为什么这个查询无法编译：

错误1属性'<> h__TransparentIdentifier0'不能与类型参数

 
 public class Program 
 {
 public static void Main（string [] args）
 {
 var docs = new dynamic [0]; 
 var q = from doc in docs 
其中doc [@ metadata] [Raven-Entity-Name] ==Cases
其中doc.AssociatedEntities！= null 
从实体在doc.AssociatedEntities 
其中entity.Tags！= null // COMPILER ERROR HERE 
从标签在entity.Tags 
其中tag.ReferencedAggregate！= null 
选择new {tag.ReferencedAggregate.Id，doc .__ document_id}; 
} 
} 
 
 public static class LinqOnDynamic 
 {
 private static IEnumerable< dynamic> select（this object self）
 {
 if（self == null）
 yield break; 
 if（self is IEnumerable == false || self is string）
 throw new InvalidOperationException（尝试枚举+ self.GetType（）。Name）; 
 
 foreach（var item in（（IEnumerable）self））
 {
 yield return item; 
} 
} 
 
 public static IEnumerable< dynamic> SelectMany（这个对象源，
 Func< dynamic，int，IEnumerable< dynamic>> collectionSelector，
 Func< dynamic，dynamic，dynamic> resultSelector）
 {
 return枚举。 SelectMany（Select（source），collectionSelector，resultSelector）; 
} 
 
 public static IEnumerable< dynamic> SelectMany（此对象源，
 Func< dynamic，IEnumerable< dynamic>> collectionSelector，
 Func<动态，动态> resultSelector）
 {
 return Enumerable.SelectMany选择（来源），collectionSelector，resultSelector）; 
} 
 
 public static IEnumerable< dynamic> selectMany（此对象源，
 Func< object，IEnumerable< dynamic>>选择器）
 {
 return Select（source）.SelectMany< object，object>（selector）; 
} 
 
 public static IEnumerable< dynamic> selectMany（此对象源，
 Func< object，int，IEnumerable< dynamic>>选择器）
 {
 return Select（source）.SelectMany< object，object>（selector）; 
 
} 
} 
 

为了增加侮辱伤害，以下作品：

 
 var docs = new dynamic [0]; 
 var q = from doc in docs 
其中doc [@ metadata] [Raven-Entity-Name] ==Cases
其中doc.AssociatedEntities！= null 
 from entity in doc.AssociatedEntities 
其中entity.Tags！= null 
来自entity.Tags中的标签
 select new {tag.ReferencedAggregate.Id，doc .__ document_id}; 
 

只有当我添加：

其中tag.ReferencedAggregate！= null

我之前收到两行错误：

其中entity.Tags！= null // COMPILER

不知道发生了什么

解决方案

如果我尝试将您的电话转换为：

  var q = from doc in docs.Where（doc => doc [@ metadata ] [Raven-Entity-Name] ==Cases|| doc.AssociatedEntities！= null）
来自doc.AssociatedEntities.Where中的实体（entity => entity.Tags！= null）
  

我收到一个不同的编译器错误，这可能揭示了发生了什么：

'不能使用lambda表达式作为动态调度操作的参数，而无需首先将其转换为委托或表达式树类型'

所以我猜测你必须重载Where运算符。

I'll say up front that I am doing some really scary things with linq on dynamic data. But I can't figure out why this query fails to compile:

Error 1 The property '<>h__TransparentIdentifier0' cannot be used with type arguments

public class Program
{
    public static void Main(string[] args)
    {
        var docs = new dynamic[0];
        var q = from doc in docs
                where doc["@metadata"]["Raven-Entity-Name"] == "Cases"
                where doc.AssociatedEntities != null
                from entity in doc.AssociatedEntities
                where entity.Tags != null // COMPILER ERROR HERE
                from tag in entity.Tags
                where tag.ReferencedAggregate != null
                select new {tag.ReferencedAggregate.Id, doc.__document_id};
    }
}

public static class LinqOnDynamic
{
    private static IEnumerable<dynamic> Select(this object self)
    {
        if (self == null)
            yield break;
        if (self is IEnumerable == false || self is string)
            throw new InvalidOperationException("Attempted to enumerate over " + self.GetType().Name);

        foreach (var item in ((IEnumerable) self))
        {
            yield return item;
        }
    }

    public static IEnumerable<dynamic> SelectMany(this object source,
                                                    Func<dynamic, int, IEnumerable<dynamic>> collectionSelector,
                                                    Func<dynamic, dynamic, dynamic> resultSelector)
    {
        return Enumerable.SelectMany(Select(source), collectionSelector, resultSelector);
    }

    public static IEnumerable<dynamic> SelectMany(this object source,
                                                    Func<dynamic, IEnumerable<dynamic>> collectionSelector,
                                                    Func<dynamic, dynamic, dynamic> resultSelector)
    {
        return Enumerable.SelectMany(Select(source), collectionSelector, resultSelector);
    }

    public static IEnumerable<dynamic> SelectMany(this object source,
                                                    Func<object, IEnumerable<dynamic>> selector)
    {
        return Select(source).SelectMany<object, object>(selector);
    }

    public static IEnumerable<dynamic> SelectMany(this object source,
                                                                    Func<object, int, IEnumerable<dynamic>> selector)
    {
        return Select(source).SelectMany<object, object>(selector);

    }
}

To add insult to injury, the following works:

var docs = new dynamic[0];
var q = from doc in docs
        where doc["@metadata"]["Raven-Entity-Name"] == "Cases"
        where doc.AssociatedEntities != null
        from entity in doc.AssociatedEntities
        where entity.Tags != null
        from tag in entity.Tags
        select new { tag.ReferencedAggregate.Id, doc.__document_id };

It is only when I add:

where tag.ReferencedAggregate != null

That I get an error two lines before:

where entity.Tags != null // COMPILER ERROR HERE

Not sure what is going on

解决方案

If I try just converting your calls to:

var q = from doc in docs.Where(doc => doc["@metadata"]["Raven-Entity-Name"] == "Cases" || doc.AssociatedEntities != null)
        from entity in doc.AssociatedEntities.Where(entity => entity.Tags != null)

I get a different compiler error which perhaps reveals what is going on:

'Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type'

So I guess you have to overload the Where operator.

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