Question

您好我有两个实体模型，表中的数据为：

Table Group
id    name
1     NW
2     SW
3     NE

Second Table is 
Location
id  groupId  count
1      1      34
2      2       5
3      2       90
4      1       33
5      1       23

我想写一个linq查询或在EF中使用上下文，以便我可以按每个groupId进行分组，以便结果为

groupdId  1
    {count 34, 33, 23}
groupId 2
    {count 90,5}

我试过以下

from e in DbContext.Set<Group>()
join a in DbContext.Set<locatin>() on e.Id equals a.groupId
Select new Test
{
    groupId= e.groupdId
    tables = new List<tbl>()
    {
        count= a.count;
    }
}

public class Test  
{
    public int groupId {get; set;}
    public IEnumerable<gbl> Tables {get; set;}
}

public class tbl
{
    public int count {get; set;}
}

当我到达count=a.count时写入查询，我得到intellisense错误无法解决。请让我知道如何更正我的查询，以便我得到groupId的标题然后只有计数数字的另一个数组。感谢。

Answer 1

以下将适用于此案例：

var result =
    groups.Join(locations,g=>g.id,l=>l.groupId,(g,l)=>new {l})
          .GroupBy(x =>x.l.groupId,x=>x.l.count)
          .Select(y=>new Test
                    {
                    groupId= y.Key,
                    tables = y.Select(n => new tbl{count = n})
                    });

以下是步骤：

使用groups和locations

id

groupid

GroupBy结果并预测count
Select，结果应为IEnumerable<Test>

以下是我完整的代码，我用来创建解决方案（使用LinqPad）：

 void Main()
{
    var groups = Group.CreateList();

    var locations = Location.CreateList();

    var result =
    groups.Join(locations,g=>g.id,l=>l.groupId,(g,l)=>new {l})
          .GroupBy(x =>x.l.groupId,x=>x.l.count)
          .Select(y=>new Test
                    {
                    groupId= y.Key,
                    tables = y.Select(n => new tbl{count = n})
                    });

        result.Dump();
    } 

public class Group
{
    public int id;
    public string name;

    public static List<Group> CreateList()
    {
    return new List<Group>
        {
            new Group
            {
            id = 1,
            name = "NW"
            },
            new Group
            {
            id = 2,
            name = "SW"
            },
            new Group
            {
            id = 3,
            name = "NE"
            }
        };
    }
}

public class Location
{
    public int id;
    public int groupId;
    public int count;

    public static List<Location> CreateList()
    {
    return new List<Location>
        {
            new Location
            {
            id = 1,
            groupId = 1,
            count = 34
            },
            new Location
            {
            id = 2,
            groupId = 2,
            count = 5
            },
            new Location
            {
            id = 3,
            groupId = 2,
            count = 90
            },
            new Location
            {
            id = 4,
            groupId = 1,
            count = 33
            },
            new Location
            {
            id = 5,
            groupId = 1,
            count = 23
            }
        };
    }
}

public class Test  
{
   public int groupId {get; set;}
   public IEnumerable<tbl> tables {get; set;}
}
public class tbl
{
  public int count {get; set;}
}

在两个表之间编写linq / lambda查询以使用EF获取值

1 个答案: