C# 如何在初始化列表之前在查询中获取值_C#_Asp.net Mvc_Entity Framework

C# 如何在初始化列表之前在查询中获取值

c# asp.net-mvc entity-framework

C# 如何在初始化列表之前在查询中获取值,c#,asp.net-mvc,entity-framework,C#,Asp.net Mvc,Entity Framework,您好，我刚刚开始使用MVC i实体框架，我遇到了问题。我可以在查询中获取Val4的值吗？我想我浪费时间初始化我的列表两次 var query = from p in db.Table1 join s in db.Table2 on p.ID equals s.sID join m in db.Table3 on s.sID equals m.ID group s by p into G selec

您好，我刚刚开始使用MVC i实体框架，我遇到了问题。我可以在查询中获取Val4的值吗？我想我浪费时间初始化我的列表两次

var query = from p in db.Table1
            join s in db.Table2 on p.ID equals s.sID
            join m in db.Table3 on s.sID equals m.ID
            group s by p into G
            select new Row
            {
                Val1 = G.Key,
                Val2 = G.Sum(x => x.someVal),
                Val3 = (from Z in db.Table4
                                 join p in db.Table5 on Z.ID equals p.ZamowienieID
                                 select p.otherVal).ToList().DefaultIfEmpty(0).Sum(),
                Val4 = 0,
            };

var list = query.ToList();

list.ForEach(x => x.Val4 = ((decimal)x.Val3 / (x.Val2 + (decimal)x.Val3)) * 100});

list = list.OrderbY(x =>x.Val4).ToList();

最好使用

Val4

属性的

getter

public class Row
{
    public int Val1 { get; set; }

    public int Val2 { get; set; }

    public int Val3 { get; set; }

    public decimal Val4
    {
        get
        {
            return (decimal)Val3 / (Val2 + (decimal)Val3) *100;
        }
    }
}

查询如下所示：

var query = from p in db.Table1
            join s in db.Table2 on p.ID equals s.sID
            join m in db.Table3 on s.sID equals m.ID
            group s by p into G
            select new Row
            {
                Val1 = G.Key,
                Val2 = G.Sum(x => x.someVal),
                Val3 = (from Z in db.Table4
                                 join p in db.Table5 on Z.ID equals p.ZamowienieID
                                 select p.otherVal).ToList().DefaultIfEmpty(0).Sum()
            };
var result = query.ToList();

最好使用

Val4

属性的

getter

public class Row
{
    public int Val1 { get; set; }

    public int Val2 { get; set; }

    public int Val3 { get; set; }

    public decimal Val4
    {
        get
        {
            return (decimal)Val3 / (Val2 + (decimal)Val3) *100;
        }
    }
}

查询如下所示：

var query = from p in db.Table1
            join s in db.Table2 on p.ID equals s.sID
            join m in db.Table3 on s.sID equals m.ID
            group s by p into G
            select new Row
            {
                Val1 = G.Key,
                Val2 = G.Sum(x => x.someVal),
                Val3 = (from Z in db.Table4
                                 join p in db.Table5 on Z.ID equals p.ZamowienieID
                                 select p.otherVal).ToList().DefaultIfEmpty(0).Sum()
            };
var result = query.ToList();

可以，但不能直接在

行

初始值设定项中

以便能够在

Val4

和投影中重用

Val3

和

Val3

。如果您使用的是LINQ方法语法，那么您将使用中间匿名投影（

Select

）。在查询语法中，可以将表达式用于相同目的：

var query = from p in db.Table1
            join s in db.Table2 on p.ID equals s.sID
            join m in db.Table3 on s.sID equals m.ID
            group s by p into G
            let Val2 = G.Sum(x => x.someVal)
            let Val3 = (from Z in db.Table4
                        join p in db.Table5 on Z.ID equals p.ZamowienieID
                        select p.otherVal).DefaultIfEmpty(0).Sum()
            let Val4 = ((decimal)x.Val3 / (x.Val2 + (decimal)x.Val3)) * 100
            orderby Val4
            select new Row
            {
                Val1 = G.Key,
                Val2 = Val2,
                Val3 = Val3,
                Val4 = Val4,
            };