C#LINQ查询填充元组列表 [英] c# LINQ query filling a Tuple List

问题描述

我需要在Linq to Entities的帮助下使用MSSQL数据库中的值填充元组列表.下面的代码片段将有助于获得一个元组列表，其中1个数据库行反映了1个元组条目.如果为calculateData有3行，我们将在该列表中使用Field1至Field4创建3个元组条目.

I need to fill a Tuple-List with values from a MSSQL-Database with help of Linq to Entities. The code snippet below will help to get a Tuple-List where 1 Database row reflects 1 Tuple Entry. In case there are 3 rows for calculateData we would get 3 Tuple Entries in that list created with Field1 to Field4.

下面的代码使之成为可能:

The code below makes it possible:

var queryResult = (from a in calculate
                   join b in calculateData on a.Id equals b.CalcId into c
                   where a.SpecialID == 2023 && a.VersionId == 1
                   orderby a.InternalOrderNr ascending
                   select new
                   {
                        a.Field1,
                        a.Field2,
                        a.Field3,
                        myField4 = c.Select(d => new {
                                    d.Field1, d.Field2, d.Field3, d.Field4})
                    }).ToList();

var result = queryResult.Select(r => new Storage
{
    myField1 = r.Field1,
    myField2 = r.Field2,
    myField3 = r.Field3,
    myField4 = r.myField4.Select(t => new Tuple<int,int,decimal,string>
        (
            t.Field1,
            t.Field2,
            t.Field3,
            t.Field4)
        ).ToList()
});

return result;

但是我需要的有点不同.我在列表中总共9个元组条目中需要这3个数据库行.示例:

But what I need is a bit different. I need for those 3 database rows in total 9 Tuple Entries in the list. Example:

数据库每行包含4列(Column1，Column2，Column3，Column4).
我们有3行.

Database contains 4 Columns (Column1, Column2, Column3, Column4) per row.
And we have 3 Rows.

元组1:DB-Row1和Column1，Column2、0、0
元组2:DB-Row1和Columm2，列3，0，1
元组3:DB-Row1和Columm3，列4，0，2
元组4:DB-Row2和Column1，Column2、1、0
元组5:DB-Row2和Columm2，列3，1，1
元组6:DB-Row2和Columm3，列4，1，2
元组7:DB-Row3和Column1，Column2、2、0
元组8:DB-Row3和Columm2，列3，2，1
元组9:DB-Row3和Columm3，列4，2，2

Tuple 1: DB-Row1 and Column1, Column2, 0, 0
Tuple 2: DB-Row1 and Columm2, Column3 ,0 ,1
Tuple 3: DB-Row1 and Columm3, Column4 ,0 ,2
Tuple 4: DB-Row2 and Column1, Column2, 1, 0
Tuple 5: DB-Row2 and Columm2, Column3 ,1 ,1
Tuple 6: DB-Row2 and Columm3, Column4 ,1 ,2
Tuple 7: DB-Row3 and Column1, Column2, 2, 0
Tuple 8: DB-Row3 and Columm2, Column3 ,2 ,1
Tuple 9: DB-Row3 and Columm3, Column4 ,2 ,2

所以这里的区别在于，数据库行和元组之间没有1:1的映射.我需要从1个数据库行中创建几个元组.在上面的示例中，我们有3个元组条目，但可以有所不同，也可以更多或更少.

So the difference here is that there is not a 1:1 Mapping between database row and Tuple. I need to make several Tuple out of 1 Database row. In the example above we have 3 Tuple entries, but it can differ and can be more or less.

推荐答案

我猜类似的东西应该对您有用:

I guess something like this should work for you:

var queryResult = (from a in calculate
                   join b in calculateData on a.Id equals b.CalcId into c
                   where a.SpecialID == 2023 && a.VersionId == 1
                   orderby a.InternalOrderNr ascending
                   select new
                   {
                        a.Field1,
                        a.Field2,
                        a.Field3,
                        myField4 = c.Select(d => new {
                                    d.Field1, d.Field2, 
                                    d.Field3, d.Field4
                                    d.Field5, d.Field6})
                    }).ToList();

var result = queryResult.Select(r => new Storage
{
    myField1 = r.Field1,
    myField2 = r.Field2,
    myField3 = r.Field3,
    myField4 = r.myField4.SelectMany(t => new [] 
    {
        Tuple<int,int>(t.Field1, t.Field2),
        Tuple<int,int>(t.Field3, t.Field4),
        Tuple<int,int>(t.Field5, t.Field6)
    }).ToList()
}).ToList();

return result;

具有双'foreach'循环的替代版本应以相同的方式工作，但不会创建元组的冗余数组:

Alternative version with double 'foreach' loop should work in the same way but it will not create redundant arrays of tuples:

var queryResult = (from a in calculate
                   join b in calculateData on a.Id equals b.CalcId into c
                   where a.SpecialID == 2023 && a.VersionId == 1
                   orderby a.InternalOrderNr ascending
                   select new
                   {
                        a.Field1,
                        a.Field2,
                        a.Field3,
                        myField4 = c.Select(d => new {
                                    d.Field1, d.Field2, 
                                    d.Field3, d.Field4
                                    d.Field5, d.Field6})
                    }).ToList();

var result = new List<Storage>();
foreach(var row in queryResult){
  var storage = new Strorage
  {
    myField1 = r.Field1,
    myField2 = r.Field2,
    myField3 = r.Field3,
    myField4 = new List<Tuple<int,int>>()
  };
  foreach(var subRow in row.myField4)
  {
    storage.myField4.Add(Tuple<int,int>(t.Field1, t.Field2));
    storage.myField4.Add(Tuple<int,int>(t.Field3, t.Field4));
    storage.myField4.Add(Tuple<int,int>(t.Field5, t.Field6));
  }
}

return result;

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