GroupJoin 操做

GroupJoin

The GroupJoin operator performs the same task as Join operator except that GroupJoin returns a result in group based on specified group key.
The GroupJoin operator joins two sequences based on key and groups the result by matching key and then returns the collection of grouped result and key.

Example

1. publicclassStudent{
2. publicintStudentID{get;set;}
3. publicstringStudentName{get;set;}
4. publicintStandardID{get;set;}
5. }
7. publicclassStandard{
8. publicintStandardID{get;set;}
9. publicstringStandardName{get;set;}
10. }
12. IList<Student> studentList =newList<Student>(){
13. newStudent(){StudentID=1,StudentName="John",StandardID=1},
14. newStudent(){StudentID=2,StudentName="Moin",StandardID=1},
15. newStudent(){StudentID=3,StudentName="Bill",StandardID=2},
16. newStudent(){StudentID=4,StudentName="Ram",StandardID=2},
17. newStudent(){StudentID=5,StudentName="Ron"}
18. };
20. IList<Standard> standardList =newList<Standard>(){
21. newStandard(){StandardID=1,StandardName="Standard 1"},
22. newStandard(){StandardID=2,StandardName="Standard 2"},
23. newStandard(){StandardID=3,StandardName="Standard 3"}
24. };
26. var groupJoin = standardList.GroupJoin(studentList,//inner sequence
27. std => std.StandardID,//outerKeySelector
28. s => s.StandardID,//innerKeySelector
29. (std, studentsGroup)=>new// resultSelector
30. {
31. Students= studentsGroup,
32. StandarFulldName= std.StandardName
33. });
35. foreach(var item in groupJoin)
36. {
37. Console.WriteLine(item.StandarFulldName);
39. foreach(var stud in item.Students)
40. Console.WriteLine(stud.StudentName);
41. }
43. // Results
44. Standard1:
45. John,
46. Moin,
47. Standard2:
48. Bill,
49. Ram,
50. Standard3: