文档：https://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b
1.可以对查询出来的结果做一些转换，下面的例子在数组中查找以"B"开头的名字，然后全部转成小写输出
string[] names = { "Jack", "Bob", "Bill", "Catty", "Willam" };
var rs = from n in names
where n.StartsWith("B")
select n.ToLower();
foreach (var item in rs)
{
Response.Write(item+"<br />");
}
2.返回匿名类型，只返回需要的信息
var users = from c in UserList
where c.Mobile.StartsWith("135")
select new
{
Name = c.Name,
Contact = c.Address + " " + c.Mobile
};
3.使用原数组，产生两组新数组
public void Linq9()
{
string[] words = { "aPPLE", "BlUeBeRrY", "cHeRry" };
var upperLowerWords =
from w in words
select new { Upper = w.ToUpper(), Lower = w.ToLower() };
foreach (var ul in upperLowerWords)
{
Console.WriteLine("Uppercase: {0}, Lowercase: {1}", ul.Upper, ul.Lower);
}
}
4.判断数字是否与他的下标一致
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsInPlace = numbers.Select((num, index) => new { Num = num, InPlace = (num == index) });
Console.WriteLine("Number: In-place?");
foreach (var n in numsInPlace)
{
Response.Write(string.Format("{0}: {1}<br />", n.Num, n.InPlace));
}
5.获得A小于B的所有可能的集合，返回 拿A中的每个元素和B中的每个元素对比的结果
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var pairs =
from a in numbersA
from b in numbersB
where a < b
select new { a, b };
Console.WriteLine("Pairs where a < b:");
foreach (var pair in pairs)
{
Console.WriteLine("{0} is less than {1}", pair.a, pair.b);
}
6.从一个集合的子集中过滤，金额小于500的订单
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.Total < 500.00
select new { c.CustomerID, o.OrderID, o.Total };
7.查询所有大于指定日期的用户订单
List<Customer> customers = GetCustomerList();
var orders = from c in customers from o in c.Orders where o.OrderDate >= new DateTime(1998, 1, 1) select new { c.CustomerID, o.OrderID, o.OrderDate };
延伸：
List<Customer> customers = GetCustomerList();
DateTime cutoffDate = new DateTime(1997, 1, 1);
var orders =
from c in customers
where c.Region == "WA"
from o in c.Orders
where o.OrderDate >= cutoffDate
select new { c.CustomerID, o.OrderID };
8.代替二重for循环
参考：http://www.cnblogs.com/manupstairs/archive/2012/11/27/2790114.html
http://www.cnblogs.com/lyout/archive/2012/11/28/2792622.html
List<Customer> customers = GetCustomerList();
var customerOrders =
customers.SelectMany(
(cust, custIndex) =>
cust.Orders.Select(o => "Customer #" + (custIndex + 1) + " has an order with OrderID " + o.OrderID));
原文：http://www.cnblogs.com/xsj1989/p/5203678.html