Linq left outer join

Question

I ultimately what I needed is generic function which would take two datatable and and 2 tablekeys and return Joined datatable. So here is my first step to solve it.

How Can I write Linq example of following T-SQL example in VB?

SELECT * FROM
Table1
LEFT OUTER JOIN
Table2
ON Table1.key = Table2.key

score 3 · Accepted Answer · edited Oct 15 '17 at 17:29

3

It would be something like this:

Dim JoinedResult = From t1 In Table1 
    Group Join t2 In Table2 
       On t1.key Equals t2.key 
       Into RightTableResults = Group 
    From t2 In RightTableResults.DefaultIfEmpty 
    Select t1.Prop1, 
       t2.Prop2

I'm not a VB guy (anymore), but I think this would work.

edited Oct 15 '17 at 17:29

vbjay

107
10

answered Apr 21 '11 at 07:27

Mikael Östberg

16,982
6
61
79

Thanks for the answer. I got little confused here. what are the Prop1 and Prop2? are they columns? Issue i'm having is I can't select the columns since I'm tryting to write generic function. – Gubi Apr 21 '11 at 09:01
`Prop1` and `Prop2` were just example columns on your tables. Reading your question again I can see that you want a generic function. I'll try to think of something. – Mikael Östberg Apr 21 '11 at 09:58

score 0 · Answer 2 · answered Apr 21 '11 at 14:04

You can simply use the existing Join method

public static IEnumerable<TResult> Join<TOuter, TInner, TKey, TResult>(
    this IEnumerable<TOuter> outer,
    IEnumerable<TInner> inner,
    Func<TOuter, TKey> outerKeySelector,
    Func<TInner, TKey> innerKeySelector,
    Func<TOuter, TInner, TResult> resultSelector
)

eg:

table1.Join(table2, t1 => t1.Key, t2 => t2.Key, (t1, t2) => new { Table1 = t1, Table2 = t2 });

can find more overloads and examples http://msdn.microsoft.com/en-us/library/system.linq.enumerable.join.aspx

Pardon me for c# examples

this is not left outer join btw – almog.ori Apr 21 '11 at 14:12 — almog.ori, Apr 21 '11 at 14:12

Linq left outer join

2 Answers2

Linked