melo 唐

1.select 查詢且合併欄位

var result =

      from mySet in myList

      select "ID:"+mySet.StudentId + "," +"Name:"+mySet.StudentName;

注意的地方:

• 一次傳回 StudentID 和 StudentName 欄位合併的字串。

2.傳回匿名型別的LINQ查詢

此種查詢方法比上面方法更為靈活,它是一次傳回一個資料子集。 

var result =

from mySet in myList
select new
{
Name = mySet.StudentId + "," + mySet.StudentName,
myAddress = mySet.Address
};

注意的地方:

• 1.result 會收到{ Name = 1,Manish, myAddress = Hyderabad }這樣的資料集。 
• 2.查詢回傳給 result 其實是 IEnumerable,其型別為一種新型別:包含屬性Name和myAddress。 

3.使用 WHERE 篩選資料

var result =

from mySet in myList
where mySet.Address == "Hyderabad"
select new { mySet.StudentId, mySet.StudentName };

注意的地方:

• 1.首先會先執行where子句,再對得到的可列舉(Enumerable)集合執行Select子句,
• 2.其回傳結果為一個包含StudentId及StudentName之匿名型別。

4.使用 WHERE 篩選資料+篩選學生姓名開頭為"M"

var result =

from mySet in myList
where mySet.StudentName.StartsWith("M")
select mySet.StudentName;

注意的地方:

• StartsWith

5.對資料排序-OrderBy,依照ID遞減排序找出學生姓名

var result =

from mySet in myList
orderby mySet.StudentId descending
select mySet.StudentName;

注意的地方:

• descending

6.對資料群組-Group by,依照電話分群組

var result =

from mySet in myList
group mySet by mySet.MobileNo;

注意的地方:

• group mySet by mySet.MobileNo
• 對mySet資料集依照MobileNo做Group。 

7.Group by分兩群組,此查詢會把MobileNo和Address相同放同一組

var result =

from mySet in myList
group mySet by new { mySet.MobileNo, mySet.Address };

注意的地方:

• group mySet by new { mySet.MobileNo, mySet.Address }; 
• 所以ID:1,Name:Manish , ID:2,Name:Venkat 放入同一組

8.Join:可以將兩個不同類別組合再一起(這裡只是為了方便才把Student2弄得這麼像Student類別)

var result =

from mySet in myList
join mySet2 in myList2
on mySet.StudentId equals mySet2.StudentId2
select new
{
mySet.StudentId,
mySet.StudentName,
mySet2.StudentId2,
mySet2.StudentName2
};

注意的地方:

•  mySet.StudentId equals mySet2.StudentId2

完整程式碼:

https://drive.google.com/open?id=

0B1K8K3aq2Hqbd203YjQ3UXFFNDQ&authuser=0