Merge Multiple Rows in SQL Server

I was just going through a problem in database which was related to querying data from two tables but all the uncommon columns should be merged to a single row even comma separated.

Primary Table

ID	Value_1	Value_2
1	ABC	DEF
2	GEH	IJK

Foreign Table

ID	FK_ID	Value_1
1	1	LMK
2	1	IJKK
3	2	ZZZ
4	2	YYY

 Expected Result

PK.ID	FK_ID	PK.Value_1	FK_Value_1	PK.Value_2
1	1122,2122	ABC	LMK,IJKK	LKM
2	3122,4122	GEH	ZZZ,YYY	NOP

Query

Select PK.ID,PK.Value_1, PK.Value_2,

      (SELECT STUFF( (SELECT ', ' +  CONVERT(varchar(25), FK.ID, 1) 

            FROM FOREIGN_TABLE FK  WHERE FK.ID=PK.ID

                  FOR XML PATH ('')) , 1, 2, ''))   AS FK_ID ,

      (SELECT STUFF( (SELECT ', ' +  CONVERT(varchar(25), FK2.Value_1, 1)

             FROM FOREIGN_TABLE FK2 WHERE FK2.ID=PK.ID 

                  FOR XML PATH ('')) , 1, 2, ''))   AS FK_Value_1 

FROM PRIMARY_TABLE PK 

This query will be performance wise slow but, in SQL Server we don't have group concat like MySQL so, we will have to bear the pain.