如何将此SQL查询转换为lambda表达式

Question

SELECT [t0].[Id], 
       [t0].[Challan_No], 
       [t0].[Type], 
       [t0].[Measurement], 
       [t0].[Update_By], 
       [t0].[Date], 
       [t1].[Id] AS [Id2], 
       [t1].[Challan_No] AS [Challan_No2], 
       [t1].[Own_Comany], 
       [t1].[Parti_Name], 
       [t1].[Update_By] AS [Update_By2], 
       [t1].[Date] AS [Date2], 
       [t1].[IsDelete], 
       [t1].[Isgenbill], 
       [t2].[Rate] AS [Rate1]
FROM [dbo].[Challan_Total] AS [t0]
INNER JOIN [dbo].[Challan] AS [t1] ON [t0].[Challan_No] = [t1].[Challan_No]
INNER JOIN [dbo].[Rate] AS [t2] ON [t0].[Type] = [t2].[Meterial_type] 
                                AND [t1].Own_Comany = [t2].Company_Id 
                                AND [t1].Parti_Name=[t2].Parti_Id
WHERE [t0].[Challan_No] = '2014CH 10002'

以下是我提出的建议：

var getch = dm.Challan_Totals.Where(m => m.Challan_No == "")
                    .Join(dm.Challans,
                    c => c.Challan_No, d => d.Challan_No,
                    (c, d) => new { c, d }).Select(b => b)
                    .Join(dm.Rates, 
                    r => r.c.Type && r.d.Own_Comany && r.d.Parti_Name ,
                    s => s.Meterial_type && s.Company_Id && s.Parti_Id,
                   (r, s) => new { r, s.Rate1 });

Answer 1

我认为这会给你你想要的东西：

var result = from t0 in ChallanTotal
             join t1 in Challan on t0.Challan_No equals t1.Challan_No
             join t2 in Rate on new { COL1 = t0.Type, COL2 = t1.Own_Comany, COL3 = t1.Parti_Name }
                                equals
                                new { COL1 = t2.Meterial_type, COL2 = t2.Company_Id, COL3 = t2.Parti_Id }
             where t0.Challan_No == "2014CH 10002"
             select new
             {
                 Id = t0.Id,
                 Challan_no = t0.Challan_No,
                 Type = t0.Type,
                 Id2 = t1.Id,
                 Challan_No2 = t1.Challan_No,
                 Own_Company = t1.Own_Comany,
                 Rate1 = t2.Rate1   
             };

这是使用扩展方法的等效表达式：

var result = ChallanTotal.Join(Challan,
                               ct => ct.Challan_No ,
                               c => c.Challan_No,
                               (ct, c) => new { ct, c })
                         .Join(Rate,
                               ctc => new 
                               { 
                                  Type = ctc.ct.Type, 
                                  Own_Company = ctc.c.Own_Comany, 
                                  Parti_Name = ctc.c.Parti_Name 
                               },
                               rt => new 
                               { 
                                  Type = rt.Meterial_type, 
                                  Own_Company = rt.Company_Id, 
                                  Parti_Name = rt.Parti_Id 
                               },
                               (ctc, rt) => new {ctc, rt})
                         .Where(x => x.ctc.ct.Challan_No == "2014CH 10002")
                         .Select(res => new { Id = res.ctc.ct.Id,
                                              Challan_no = res.ctc.ct.Challan_No,
                                              Type = res.ctc.ct.Type,
                                              Id2 = res.ctc.c.Id,
                                              Challan_No2 = res.ctc.c.Challan_No,
                                              Own_Company = res.ctc.c.Own_Comany,
                                              Rate1 = res.rt.Rate1   
                                            });

加入多列时的关键点是：

1. 列类型必须相同，并且
2. 列名称也必须相同。

P.S。我没有在上面的代码中包含所有列，但可以自己轻松添加。

修改

上面的查询已经过测试，可以使用以下模型运行：

类似于SQL Schema的类模型：

class Challan_Total
{
    public int Id {get; set;}
    public string Challan_No {get; set;}
    public string Type {get; set;}
}

class Challan
{
    public int Id { get; set; }
    public string Challan_No {get; set;}
    public string Own_Comany {get; set;}
    public string Parti_Name {get; set;}
}

class Rate
{
    public string Company_Id {get; set;}
    public string Parti_Id {get; set;}
    public string Meterial_type { get; set;}
    public string Rate1 { get; set; }
}

示例数据：

List<Challan_Total> lstChallanTotal = new List<Challan_Total>()
{
    new Challan_Total { Challan_No = "1", Id = 1, Type = "1"},
    new Challan_Total { Challan_No = "2", Id = 1, Type = "1"},
    new Challan_Total { Challan_No = "3", Id = 2, Type = "2"}
};

List<Challan> lstChallan = new List<Challan>()
{
    new Challan { Id = 1, Challan_No = "1", Own_Comany = "1", Parti_Name = "1"},
    new Challan { Id = 2, Challan_No = "2", Own_Comany = "1", Parti_Name = "2"},
    new Challan { Id = 3, Challan_No = "3", Own_Comany = "3", Parti_Name = "3"}
};

List<Rate> lstRate = new List<Rate>() 
{ 
    new Rate { Company_Id = "1", Parti_Id = "1", Meterial_type = "1", Rate1 = "p1"},
    new Rate { Company_Id = "2", Parti_Id = "1", Meterial_type = "1", Rate1 = "p2" },
    new Rate { Company_Id = "3", Parti_Id = "2", Meterial_type = "2", Rate1 = "p3" }
};