如何将IEnumerable <t>或IQueryable <t>转换为EntitySet <t>？

Question

在这种情况下,我尝试使用LINQ to XML和LINQ to SQL从XML文件导入数据到数据库.

这是我的LINQ数据模型:

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;
}

基本上我正在尝试做的是编写一个查询,它将为我提供一个数据结构,我可以提交给我的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()
                };

问题出在子查询中.我必须以某种方式将我的对象集合放入EntitySet容器中.我无法施放它(哦,我已经尝试过了)并且没有EntitySet()构造函数似乎有所帮助.

那么,我可以编写一个LINQ查询,用我的IEnumerable <Page>数据填充EntitySet <PageContent>数据吗？

Answer 1

你可以使用辅助类从IEnumerable构造你的实体集,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;
    }
}

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()