How to return Wrapper obj of TableOjb1 and TableObj2 using linq
class TableObj1 {
public string Id {get; set;}
public string Name {get; set;}
}
class TableObj2 {
public string Id {get; set;}
public string Email {get; set;}
}
class MergeObj {
public TableObj1 Obj1 {get; set;}
public TableObj2 Obj2 {get; set;}
}
My question is how to return a list of MergeObj when joining the two tables. I tried:
public IEnumerable<MergeObj> QueryJoin() {
return (
from obj1 in conn.Table<TableObj1>()
join obj2 in conn.Table<TableObj2>()
on obj1.Id
equals obj2.Id
select new MergeObj{Obj1 = obj1, Obj2 = obj2}
);
}
void main() {
IEnumerable<MergeObj> mergeObjs = QueryJoin();
}
But QueryJoin() gives Exception: System.NotSupportedException, Joins are not supported.
please note I'm using sqlite.net not ADO.net.
Try doing the select after casting the join result to a list.
public IEnumerable<MergeObj> QueryJoin()
{
List<TableObj1> t1 = conn.Table<TableObj1>().ToList();
List<TableObj2> t2 = conn.Table<TableObj2>().ToList();
return t1.Join(t2, outer => outer.Id,
inner => inner.Id,
(outer, inner) => new MergeObj { Obj1 = outer, Obj2 = inner });
}
Edit : Since your database don't seems to support join, you can extract the result of your database in two distinct List and then join them using LINQ.
您可能需要投影到匿名类型，然后使用Linq-to-Objects创建对象：
public IEnumerable<MergeObj> QueryJoin() {
return (
from obj1 in conn.Table<TableObj1>()
join obj2 in conn.Table<TableObj2>()
on obj1.Id
equals obj2.Id
select new {obj1, obj2}
).AsEnumerable()
.Select(o => new MergeObj{Obj1 = o.obj1, Obj2 = o.obj2}) ;
}
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