如何解决可能不是抽象的，必须包含一个默认构造函数？

问题描述

我有一个数据库 [![as this picture][1]][1]

我想从这个数据库中获取一个图表，当我尝试在控制器端使用 sql 查询时，出现了这样的错误； [![这是错误类型][2]][2]
这是我的控制器代码；

 public ActionResult Index2(String makineadi,DateTime? startdate,DateTime? enddate)
        {
            var data = entities.Database.sqlQuery<DataPoint>("SELECT Sıcaklık,Recete_Sure From Recete Where Machine_IP ='" + makineadi + "' and Tarih between'"+startdate+"' and '"+enddate+"'").ToList();
            ViewBag.DataPoints = JsonConvert.SerializeObject(data);
            return View();
        }

这是我的类定义，用于将图表转换为 JSON 序列化；

 [DataContract]
        public class DataPoint
        {
            public DataPoint(int Sıcaklık,int Recete_Sure)
            {
                this.Sıcaklık = Sıcaklık;
                this.Recete_Sure = Recete_Sure;
            }

            //Explicitly setting the name to be used while serializing to JSON.
            [DataMember(Name = "Sıcaklık")]
            public Nullable<int> Sıcaklık { get; set; }

        //Explicitly setting the name to be used while serializing to JSON.
        [DataMember(Name = "Recete_Sure")]
            public Nullable<int> Recete_Sure { get; set; }
        }

我该怎么做才能修复它？ [1]：https://i.stack.imgur.com/ObwWR.png [2]：https://i.stack.imgur.com/zQNgO.png

解决方法

在类中添加默认构造函数。

[DataContract]
public class DataPoint
{
    public DataPoint()
    {
    }
    public DataPoint(int Sıcaklık,int Recete_Sure)
    {
        this.Sıcaklık = Sıcaklık;
        this.Recete_Sure = Recete_Sure;
    }

    //Explicitly setting the name to be used while serializing to JSON.
    [DataMember(Name = "Sıcaklık")]
    public Nullable<int> Sıcaklık { get; set; }

    //Explicitly setting the name to be used while serializing to JSON.
    [DataMember(Name = "Recete_Sure")]
    public Nullable<int> Recete_Sure { get; set; }
}

它会解决问题