从标准的其他列表中删除列表项

Question

我有一份作家名单.

public class Writers{   
    long WriterID { get;set; }
}

我还有两个类型文章列表.

public class Article{
    long ArticleID { get; set; }
    long WriterID { get; set; }
    //and others    
}

所以我的代码是:

List<Article> ArticleList = GetList(1);
List<Article> AnotherArticleList = AnotherList(2);
List<Writers> listWriters = GetAllForbiddenWriters();

我想删除这些记录从ArticleList,AnotherArticleList其中WriterID来自匹配listWriters WriterID.如何在LINQ中执行此操作？

Answer 1

如果您确实得到了一个List<T>,我建议您List<T>.RemoveAll在构建一组编写器ID之后使用它:

HashSet<long> writerIds = new HashSet<long>(listWriters.Select(x => x.WriterID));

articleList.RemoveAll(x => writerIds.Contains(x.WriterId));
anotherArticleList.RemoveAll(x => writerIds.Contains(x.WriterId));

如果您确实想使用LINQ,可以使用:

articleList = articleList.Where(x => !writerIds.Contains(x.WriterId))
                         .ToList();
anotherArticleList = anotherArticleList
                         .Where(x => !writerIds.Contains(x.WriterId))
                         .ToList();

请注意,这会更改变量但不会修改现有列表 - 因此,如果对同一列表有任何其他引用,则它们将不会看到任何更改.(而RemoveAll修改现有列表.)

Answer 2

articlesList.RemoveAll(a => listWriters.Exists(w => w.WriterID == a.WriterID));
anotherArticlesList.RemoveAll(a => listWriters.Exists(w => w.WriterID == a.WriterID));

Answer 3

您可以使用除外：

List<car> list1 = GetTheList();
List<car> list2 = GetSomeOtherList();
List<car> result = list2.Except(list1).ToList();