Question

我有这样的EF模型：

 public class foo
    {
        private static TimeZoneInfo INDIAN_ZONE = TimeZoneInfo.FindSystemTimeZoneById("India Standard Time");
        DateTime indianTime = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, INDIAN_ZONE);
        testData tD;

        public foo(testData localtD)
        {
            this.tD = localtD;
        }

        public String Name {
            get { return tD.Name; }
            set { }
        }
        public Double dueInDays { 
            get { return (indianTime - tD.StartDate).TotalDays; }
            set { } }
    }

我的API方法是

        [Route("api/getSingleData")]
        [HttpGet]

        public dynamic getTestData()
        {

            var dataset2 = (from recordset in db.testDatas
                            select new foo(recordset) 
                            );
            return new { data = dataset2 };

        }

在db.testDatas我有日期字段，我想返回当前日期和开始日期之间的差异。

该数据库或多或少已完成，我无法对其进行更改以在db查询级别满足此要求。我为错误做的根本错误是什么

LINQ中仅支持无参数构造函数和初始值设定项到实体

要弹出？

更重要的是，我应该如何修改代码以达到要求？

感谢。

Answer 1

你无法做你想做的事。这就像你要得到的一样好......

public class foo
{
    private static TimeZoneInfo INDIAN_ZONE = TimeZoneInfo.FindSystemTimeZoneById("India Standard Time");
    DateTime indianTime = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, INDIAN_ZONE);
    string _name;
    DateTime _startDate;

    public foo()
    {
    }

    public String Name {
        get { return _name; }
        set { _name = value; }
    }

    public Double dueInDays 
    { 
        get { return (indianTime - _startDate).TotalDays; }
    }

    public DateTime StartDate
    {
        get { return _startDate; }
        set { _startDate = value; }
    }
}

API方法： -

[Route("api/getSingleData")]
[HttpGet]
public dynamic getTestData()
{
    var dataset2 = (from recordset in db.testDatas
                    select new foo
                    { 
                        Name = recordset.Name, 
                        StartDate = recordset.StartDate 
                    });
    return new { data = dataset2 };
}

或者你可以按原样保留foo并做....

[Route("api/getSingleData")]
[HttpGet]
public dynamic getTestData()
{

    var dataset2 = (from recordset in db.testDatas
                    select recordset 
                    ).ToList();

    return new { data = dataset2.select(r => new foo(r); };
}

Answer 2

您是否尝试过使用分部类来创建计算字段。类似的东西：

    public partial class testDatas
{
    public int duInDays
    {
        get 
        {
            TimeZoneInfo INDIAN_ZONE = TimeZoneInfo.FindSystemTimeZoneById("India Standard Time");
            DateTime indianTime = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, INDIAN_ZONE);
            return (indianTime - StartDate).TotalDays;
        }
    }
}

LINQ to Entities的构造函数中的参数

2 个答案: