Question

我有以下课程作为清单；

class list_TA
{
    public DateTime SAMPLE_TIME { get; set; }
    public string WAIT_CLASS { get; set; }
    public double COUNT { get; set; }

    public list_TA(DateTime SAMPLE_TIME, string WAIT_CLASS,double COUNT)
    {
        this.SAMPLE_TIME = SAMPLE_TIME;
        this.WAIT_CLASS = WAIT_CLASS;
        this.COUNT = COUNT;
    }
}

//SECOND PART

                 var test = listASH
                          .Select(g => new
                          {
                              SAMPLE_TIME = statiClass.By15Seconds(Convert.ToDateTime(g.SAMPLE_TIME)),
                              WAIT_CLASS = g.WAIT_CLASS,
                              COUNT = 0,
                          }).GroupBy(x => new { x.SAMPLE_TIME, x.WAIT_CLASS })
                          .Select(y => new
                          {
                              SAMPLE_TIME = y.Key.SAMPLE_TIME,
                              WAIT_CLASS = y.Key.WAIT_CLASS,
                              COUNT = Math.Round(y.Count() / 15.0, 2),
                          });

我想要的是将linq结果加载到list_TA中。但是下面的代码不起作用，并且会出现以下错误；

 List<list_TA> lst = (List<list_TA>)test.ToList();

错误；

Cannot convert type 'System.Collections.Generic.List<<anonymous type: System.DateTime SAMPLE_TIME, string WAIT_CLASS, double COUNT>>' to 'System.Collections.Generic.List<vodaMon.list_TA>'

转换ToList（）;没用。

Answer 1

在匿名类不能被隐式转换为任何其它类型。

您需要使用new list_TA而不是new

将默认构造函数添加到您的list_TA类中，并使用下面的代码

  .Select(y => new list_TA
  {
      SAMPLE_TIME = y.Key.SAMPLE_TIME,
      WAIT_CLASS = y.Key.WAIT_CLASS,
      COUNT = Math.Round(y.Count() / 15.0, 2),
  });

或

  .Select(y => new list_TA (
      y.Key.SAMPLE_TIME,
      y.Key.WAIT_CLASS,
      Math.Round(y.Count() / 15.0, 2)
   ));

Answer 2

还使用new list_TA代替任意类型：实例化list_TA时，它需要DateTime SAMPLE_TIME，字符串WAIT_CLASS，双COUNT作为参数传递。为了解决这个问题，请引入无参数构造函数。

 public class list_TA
{
    public DateTime SAMPLE_TIME { get; set; }
    public string WAIT_CLASS { get; set; }
    public double COUNT { get; set; }

    public list_TA()
    {

    }

    public list_TA(DateTime SAMPLE_TIME, string WAIT_CLASS, double COUNT) 
    {
        this.SAMPLE_TIME = SAMPLE_TIME;
        this.WAIT_CLASS = WAIT_CLASS;
        this.COUNT = COUNT;
    }
}

Answer 3

您可以像下面这样在LINQ中选择list_TA：

var test = listASH
                          .Select(g => new
                          {
                              SAMPLE_TIME = statiClass.By15Seconds(Convert.ToDateTime(g.SAMPLE_TIME)),
                              WAIT_CLASS = g.WAIT_CLASS,
                              COUNT = 0,
                          }).GroupBy(x => new { x.SAMPLE_TIME, x.WAIT_CLASS })
                          .Select(y => new list_TA
                          {
                              SAMPLE_TIME = y.Key.SAMPLE_TIME,
                              WAIT_CLASS = y.Key.WAIT_CLASS,
                              COUNT = Math.Round(y.Count() / 15.0, 2),
                          }).ToList();

LinQ结果进入列表

3 个答案: