有没有什么方法可以使用 linq 查询来过滤嵌套列表，以便我最终得到经过充分过滤的列表的过滤列表？

Question

我在过滤嵌套在更大列表中的字符串列表时遇到问题。

我尝试过这样的事情：

myList.FindAll(d => d.activities.Any(i => i.type.Contains("read")));

但似乎有人正在回归

我有一个“UserData”结构，如图所示：

public class UserData

{

   public int id;

   public List<UserActivity> activities;

}

public class UserActivity

{

   public string activity;

   public string type;

}

有f.ex。两种类型的活动（“读”和“写”）

我想做的是过滤给定的内容，List<UserData> myList如图所示

List<UserData> newList = new List<UserData>();

foreach(UserData d in myList){

    UserData newD = new UserData();

    newD.id = d.id;

    newD.activities= d.activities.FindAll(i =>

i.type.Contains("read"));

    if (newD.activities.Any())

        newList.Add(newD);

}

有没有办法用 Linq 查询巧妙地做到这一点？

我想要弄清楚的是一个简短而整洁的 Linq 查询来过滤我所描述的嵌套列表......我知道这可能是一个装饰问题，但它仍然让我很困扰。

Answer 1

var newList = (from userData in myList&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;let newActivities = userData.activities.Where(i => i.type.Contains("read"))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;where newActivities.Any()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;select new UserData { id = userData.id, activities = newActivities.ToList() }).ToList();

Answer 2

我通过使用解决了这个问题：newList&nbsp;=&nbsp;myList.Where(d&nbsp;=>&nbsp;d.activities.Any(act&nbsp;=>&nbsp;act.type.Contains("read"))) &nbsp;&nbsp;&nbsp;&nbsp;.Select(d&nbsp;=>&nbsp;new&nbsp;UserData&nbsp;{&nbsp;id&nbsp;=&nbsp;d.id,&nbsp;activities&nbsp;=&nbsp;new&nbsp;List<UserActivity>(&nbsp;d.activities.FindAll(act&nbsp;=>&nbsp;act.type.Contains("read"))&nbsp;)&nbsp;}) &nbsp;&nbsp;&nbsp;&nbsp;.ToList();

Answer 3

尝试以下操作：&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;List<UserData>&nbsp;newList&nbsp;=&nbsp;myList.Select(x&nbsp;=>&nbsp;new&nbsp;UserData()&nbsp;{&nbsp;id&nbsp;=&nbsp;x.id,&nbsp;activities&nbsp;=&nbsp;x.activities.Where(y&nbsp;=>&nbsp;y.type.Contains("read")).ToList()&nbsp;}) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.Where(x&nbsp;=>&nbsp;x.activities.Count&nbsp;>&nbsp;0) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.ToList();