Question

我想问一下如何编辑集合中的项目。例如：在集合myList I（字符串名称，DateTime事件）中。我想把活动搬到明年。

我试过了：

 public class ClassEvent
    {
        public string Name { get; set; }

        public DateTime Date { get; set; }

 public ClassEvent(string name, DateTime date)
        {

            Name = name;
            Date = date;
        }

MYCLASS：

public List<ClassEvent> event= new List<ClassEvent>();
public void AddEvent(string name, DateTime MyEvent)
        {
            ClassEvent  ev = new ClassEvent(name, MyEvent.Date);
            event.Add(ev);
        }

的MainForm：

forach( var a in MyClass.event)
{
   if(a.MyEvent == DateTime.Today)
      {
           Myclass.AddEvent(a.name, a.MyEvent.AddYears(1);
}

但它不起作用。

Answer 1

您正在foreach循环中创建一个新的ClassEvent，而不是编辑您正在使用的那个。我会尝试：

forach( var a in MyClass.event)
{
  if(a.MyEvent == DateTime.Today)
   {
     a.MyEvent.AddYears(1);
   }
}

Answer 2

您无法在 foreach 循环中修改集合。使用 for loop isntead：

将添加新项目添加到集合中：

  // Pay attention: backward loop
  for(int i = MyClass.event.Count - 1; i >= 0; --i) {
    ClassEvent a = MyClass.event[i];

    if (a.MyEvent == DateTime.Today)
      Myclass.AddEvent(a.name, a.MyEvent.AddYears(1);
  }

更改集合中的现有项目：

  // Any direction forward/backward will do
  for(int i = MyClass.event.Count - 1; i >= 0; --i) {
    ClassEvent a = MyClass.event[i];

    // Just change "a", since "a" is a item in the collection already
    //TODO: Check the syntax; "MyEvent" is expected being a writeable property 
    if (a.MyEvent == DateTime.Today)  
      a.MyEvent = a.MyEvent.AddYears(1);
  }

从列表中编辑特定项目

2 个答案: