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在LINQ查询中执行强制转换

.net-3.5 linq .net c#

29

Bob Wintemberg · 技术社区 · 18 年前

是否可以在LINQ查询中执行强制转换(为了编译器)?

下面的代码并不可怕,但最好将其放入一个查询中:

Content content = dataStore.RootControl as Controls.Content;

List<TabSection> tabList = (from t in content.ChildControls
                            select t).OfType<TabSection>().ToList();

List<Paragraph> paragraphList = (from t in tabList
                                 from p in t.ChildControls
                                 select p).OfType<Paragraph>().ToList();

List<Line> parentLineList = (from p in paragraphList
                             from pl in p.ChildControls
                             select pl).OfType<Line>().ToList();

content.ChildControls 你属于那种类型 TabSection 以及所有在 t.ChildControls Paragraph ……等等。

在LINQ查询中是否有方法告诉编译器 t 在里面 from t in content.ChildControls ?

5 回复 | 直到 9 年前

1

27

Chris Ammerman 18 年前

试试这个:

from TabSection t in content.ChildControls

2

11

Lucas 18 年前

根据您尝试执行的操作,以下操作之一可能会奏效:

List<Line> parentLineList1 =
  (from t in content.ChildControls.OfType<TabSection>()
   from p in t.ChildControls.OfType<Paragraph>()
   from pl in p.ChildControls.OfType<Line>()
   select pl).ToList();

List<Line> parentLineList2 =
  (from TabSection t in content.ChildControls
   from Paragraph p in t.ChildControls
   from Line pl in p.ChildControls
   select pl).ToList();

3

2

Michael Damatov 18 年前

List<TabSection> tabList = (from t in content.ChildControls
                            let ts = t as TabSection
                            where ts != null
                            select ts).ToList();

4

1

Jared xxtesaxx 18 年前

是的,您可以执行以下操作:

List<TabSection> tabList = (from t in content.ChildControls
                            where t as TabSection != null
                            select t as TabSection).ToList();

5

1

Amy B 18 年前

这是查询方法表单。

List<Line> parentLineList =
  content.ChildControls.OfType<TabSections>()
    .SelectMany(t => t.ChildControls.OfType<Paragraph>())
    .SelectMany(p => p.ChildControls.OfType<Line>())
    .ToList();