Question

我的班级

class student   
{
    public string studentid { get; set; }
    public string groupid { get; set; }//Group id
}

我的清单

List<student> pupils = new List<student>();

在这里，我选择没有组ID的学生

var studentsWithNoGroupId = from student in pupils
                            where student.groupid =="00"
                            select student;

我想通过一个for循环，它运行的次数等于studentsWithNoGroupId.Count，并为组ID分配一些我拥有的值。（只显示如何分配每个对象就足够了）。怎么做？

或者我必须改变我的linq吗？请有人帮助我。

Answer 1

你的意思是这样的吗？

var studentsWithNoGroupId = 
from student in pupils
where student.groupid =="00"
select student;

foreach(var student in studentsWithNoGroupId)
{
  student.groupid = "x";
}

Answer 2

     pupils.Where(p => p.groupid == "00")
      .ToList()
      .ForEach( 
         p => {
                p.groupid = "whatever";
         });

编辑（在Hatsjoem暗示之后，更简单）：

pupils.FindAll(p => p.groupid == "00")
 .ForEach(p => {
    p.groupid = "whatever";
 });

Answer 3

你的专栏：

var studentsWithNoGroupId = from student in pupils
                            where student.groupid =="00"
                            select student;

创建Linq查询。此查询不会立即执行。要执行它，请尝试以下操作：

var studentsWithNoGroupIdQuery = from student in pupils
                                 where student.groupid =="00"
                                 select student;

var studentsWithNoGroupId = studentsWithNoGroupIdQuery.ToList();

foreach (var student in studentsWithNoGroupId)
{
    student.groupid = // Your logic here.
}

// Save pupils back to the database here.

ToList（）使查询执行并将结果存储在List<student>中。在迭代之前执行查询很重要，因为您正在更改正在过滤查询的同一变量groupid。

Answer 4

我不知道这是不是你要找的，但我会试一试：

var yourPupils = pupils.Where(p => p.groupid == "00")
    .Select(s => new student() { 
        studentid = s.studentid, 
        groupid = "yourCustomAssignedId" 
    }).ToList();

For-loop版本：

var numberOfPupils = pupils.Count();

for (int i = 0; i < numberOfPupils; i++)
{
    if (pupils[i].groupid == "00")
    {
        pupils[i].groupid = "yourCustomAssignedId";
    }
}

在列表中搜索匹配的对象并分配值

4 个答案: