C# 使用 LINQ 有条件地更新列表
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19930450/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
conditional Updating a list using LINQ
提问by Amit Bisht
I had a list
我有一个清单
List<Myclass> li = new List<Myclass>();
where Myclass is
Myclass在哪里
class Myclass
{
public string name {get;set;}
public decimal age {get;set;}
}
items in li looks like
li 中的项目看起来像
i want to update `li` according to name but with `LINQ` like
li.where(w=> w.name = "di") = li.Where(w => w.name =="di").select(s => {s.age = 10;return s;}).Tolist();
li.where(w=> w.name = "marks") = li.Where(w => w.name =="marks").select(s => {s.age = 20;return s;}).Tolist();
li.where(w=> w.name = "grade") = li.Where(w => w.name =="grade").select(s => {s.age = 10;return s;}).Tolist();
and want result which looks like this
并想要看起来像这样的结果
my code gives error can you please tell how i do this
我的代码出错了，你能告诉我是怎么做的吗
采纳答案by Kamil Budziewski
cleanerway to do this is using foreach
更简洁的方法是使用 foreach
foreach(var item in li.Where(w => w.name =="di"))
{
item.age=10;
}
回答by Baldrick
You need:
你需要：
li.Where(w=> w.name == "di").ToList().ForEach(i => i.age = 10);
Program code:
程序代码：
namespace Test
{
class Program
{
class Myclass
{
public string name { get; set; }
public decimal age { get; set; }
}
static void Main(string[] args)
{
var list = new List<Myclass> { new Myclass{name = "di", age = 0}, new Myclass{name = "marks", age = 0}, new Myclass{name = "grade", age = 0}};
list.Where(w=> w.name == "di").ToList().ForEach(i => i.age = 10);
list.ForEach(i => Console.WriteLine(i.name + ":" + i.age));
}
}
}
Output:
输出：
di:10
marks:0
grade:0
回答by Smeegs
If you really want to use linq, you can do something like this
如果你真的想使用 linq，你可以这样做
li= (from tl in li
select new Myclass
{
name = tl.name,
age = (tl.name == "di" ? 10 : (tl.name == "marks" ? 20 : 30))
}).ToList();
or
或者
li = li.Select(ex => new MyClass { name = ex.name, age = (ex.name == "di" ? 10 : (ex.name == "marks" ? 20 : 30)) }).ToList();
This assumes that there are only 3 types of name. I would externalize that part into a function to make it more manageable.
这假设只有 3 种类型的name. 我会将该部分具体化为一个函数，使其更易于管理。
回答by sivabalan
li.Where(w => w.name == "di" )
.Select(s => { s.age = 10; return s; })
.ToList();
回答by FindOut_Quran
How about
怎么样
(from k in myList
where k.id > 35
select k).ToList().ForEach(k => k.Name = "Banana");
回答by Santosh
Try Parallelfor longer lists:
尝试Parallel获取更长的列表：
Parallel.ForEach(li.Where(f => f.name == "di"), l => l.age = 10);
回答by David Donari
Try this:
尝试这个：
li.ForEach(x => x.age = (x.name == "di") ?
10 : (x.name == "marks") ?
20 : (x.name == "grade") ?
30 : 0 );
All values are updated in one line of code and you browse the List only ONE time. You have also a way to set a default value.
所有值都在一行代码中更新，您只需浏览列表一次。您还可以设置默认值。
