Dynamic+Linq编译错误？
Dynamic+Linq编译错误？
提问于 2018-02-05 00:09:48
我在Dynamic上使用Linq。但是我不明白为什么这个查询不能编译：
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);
}
}更糟的是：
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 };当我加上：
where tag.ReferencedAggregate != null
我又得到了一个错误：
where entity.Tags != null // COMPILER ERROR HERE
回答 2
Stack Overflow用户
发布于 2018-02-05 08:21:25
如果我试着：
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)我得到了一个不同的编译器错误：
'Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type'
Stack Overflow用户
发布于 2018-02-05 09:16:43
var q = from doc in docs
where doc["@metadata"]["Raven-Entity-Name"] == "Cases"
where doc.AssociatedEntities != null
from entity in
((IEnumerable<dynamic>)doc.AssociatedEntities)
.Where(entity => entity.Tags != null)
from tag in
((IEnumerable<dynamic>)entity.Tags)
.Where(tag => tag.ReferencedAggregate != null)
select new { tag.ReferencedAggregate.Id, doc.__document_id };页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100007312
复制相关文章
相似问题
腾讯云开发者
