如何解决可能不是抽象的，必须包含默认构造函数？答案

【问题标题】：How to solve may not be abstract and must be include a default constructor?如何解决可能不是抽象的，必须包含默认构造函数？
【发布时间】：2021-02-16 13:06:02
【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，我得到了这样的错误； [![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();
        }

这是我将图表转换为 JSON 序列化的类定义；

 [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; }
        }

我应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

【问题讨论】：

标签： sql asp.net-mvc charts canvasjs

【解决方案1】：

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; }
}

解决问题

【讨论】：