[英]How do you cast an IEnumerable<t> or IQueryable<t> to an EntitySet<t>?
In this situation I am trying to perform a data import from an XML file to a database using LINQ to XML and LINQ to SQL.在这种情况下,我尝试使用 LINQ 到 XML 和 LINQ 到 SQL 执行从 XML 文件到数据库的数据导入。
Here's my LINQ data model:这是我的 LINQ 数据 model:
public struct Page
{
public string Name;
public char Status;
public EntitySet<PageContent> PageContents;
}
public struct PageContent
{
public string Content;
public string Username;
public DateTime DateTime;
}
Basically what I'm trying to do is write a query that will give me a data structure that I can just submit to my LINQ Data Context.基本上我想做的是编写一个查询,该查询将为我提供一个数据结构,我可以将其提交到我的 LINQ 数据上下文。
IEnumerable<Page> pages = from el in doc.Descendants()
where el.Name.LocalName == "page"
select new Page()
{
Name = el.Elements().Where(e => e.Name.LocalName == "title").First().Value,
Status = 'N',
PageContents = (from pc in el.Elements()
where pc.Name.LocalName == "revision"
select new PageContent()
{
Content = pc.Elements().Where(e => e.Name.LocalName=="text").First().Value,
Username = pc.Elements().Where(e => e.Name.LocalName == "contributor").First().Elements().Where(e => e.Name.LocalName == "username").First().Value,
DateTime = DateTime.Parse(pc.Elements().Where(e => e.Name.LocalName == "timestamp").First().Value)
}).ToList()
};
The problem is in the sub-query.问题出在子查询中。 I have to somehow get my object collection into the EntitySet container.我必须以某种方式将我的 object 集合放入 EntitySet 容器中。 I can't cast it (oh lord how I've tried) and there's no EntitySet() constructor that would seem to help.我无法施放它(天哪,我怎么试过)而且没有 EntitySet() 构造函数似乎有帮助。
So, can I write a LINQ query that will populate the EntitySet<PageContent> data with my IEnumerable<Page> data?那么,我能否编写一个 LINQ 查询,用我的 IEnumerable<Page> 数据填充 EntitySet<PageContent> 数据?
you can construct your entity set from a IEnumerable using a helper class, something like:您可以使用帮助器 class 从 IEnumerable 构建您的实体集,例如:
public static class EntityCollectionHelper
{
public static EntitySet<T> ToEntitySet<T>(this IEnumerable<T> source) where T:class
{
EntitySet<T> set = new EntitySet<T>();
set.AddRange(source);
return set;
}
}
and use it like so:并像这样使用它:
PageContents = (from pc in el.Elements()
where pc.Name.LocalName == "revision"
select new PageContent()
{
Content = pc.Elements().Where(e => e.Name.LocalName=="text").First().Value,
Username = pc.Elements().Where(e => e.Name.LocalName == "contributor").First().Elements().Where(e => e.Name.LocalName == "username").First().Value,
DateTime = DateTime.Parse(pc.Elements().Where(e => e.Name.LocalName == "timestamp").First().Value)
}).ToEntitySet()
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