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LinqToSql初探
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内容图文
LINQ TO SQL是一种轻量级的ORM框架，它对ADO.NET进行了轻量级的封装，讲数据库原封不动的映射成模型，常用于中小型项目，优点：简单。缺点：数据库模型过于复杂时,可能不满足开发要求。
LINQ语句:
简单类型查询(string):
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Text;
namespace
LINQ
{
class
Program
{
public
delegate
int[] generateLotsOfNumbers(int count);//产生大量随机数staticvoid Main(string[] args)
{
string[] names ={"Alonso","Zheng","Smith","Jones","Smythe","Small","Ruiz","Hsieh","Jorgenson",
"Ilyich","Singh","Samba","Fatimah"};
var queryResult1 = from n in names select n;//遍历操作var queryResult2 = names;//lambda表达式，功能同1var queryResult3 = from n in names where n.StartsWith("S") select n;//查询以S开头var queryResult4 = names.Where(n => n.StartsWith("S"));// lambda表达式，功能同3var queryResult5 = from n in names where n.StartsWith("S") orderby n select n;//升序var queryResult6 = from n in names where n.StartsWith("S") orderby n descending select n;//降序var queryResult7 = names.OrderBy(n => n).Where(n => n.StartsWith("S"));//lambda表达式,功能同4var queryResult8 = names.OrderByDescending(n => n).Where(n => n.StartsWith("S"));//功能同5
//查询大型数据集
generateLotsOfNumbers ge = delegate(int count) //匿名函数 {
Random generator = new Random(0);
int[] result = newint[count];
for(int i=0;i<count;i++)
{
result[i] = generator.Next();
}
return result;
};
int[] numbers = ge(12345678);
var queryResult9 = from n in numbers where n < 1000select n;//条件查找var queryResult10 = numbers.Where(n => n < 1000);//lambda表达式，功能同9
//聚合运算符
Console.WriteLine(queryResult9.Count());//数量 Console.WriteLine(queryResult9.Min());
Console.WriteLine(queryResult9.Max());
Console.WriteLine(queryResult9.Average());
Console.WriteLine(queryResult9.Sum());
}
}
}
复杂类型查询:
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Text;
namespace
LINQ
{
class
Customer
{
public
string ID { get; set; }
publicstring City { get; set; }
publicstring Country { get; set; }
publicstring Region { get; set; }
publicdecimal Sales { get; set; }
publicoverridestring ToString()
{
return"ID: " + ID + " City: " + City + " Country: " + Country + " Region: " + Region + " Sales: " + Sales;
}
}
class Program
{
publicstaticvoid Main(string[] args)
{
List<Customer> customers = new List<Customer> {
new Customer { ID="A", City="New York", Country="USA", Region="North America", Sales=9999},
new Customer { ID="B", City="Mumbai", Country="India", Region="Asia", Sales=8888},
new Customer { ID="C", City="Karachi", Country="Pakistan", Region="Asia", Sales=7777},
new Customer { ID="D", City="Delhi", Country="India", Region="Asia", Sales=6666},
new Customer { ID="E", City="S?o Paulo", Country="Brazil", Region="South America", Sales=5555 },
new Customer { ID="F", City="Moscow", Country="Russia", Region="Europe", Sales=4444 },
new Customer { ID="G", City="Seoul", Country="Korea", Region="Asia", Sales=3333 },
new Customer { ID="H", City="Istanbul", Country="Turkey", Region="Asia", Sales=2222 },
new Customer { ID="I", City="Shanghai", Country="China", Region="Asia", Sales=1111 },
new Customer { ID="J", City="Lagos", Country="Nigeria", Region="Africa", Sales=1000 },
new Customer { ID="K", City="Mexico City", Country="Mexico", Region="North America", Sales=2000 },
new Customer { ID="L", City="Jakarta", Country="Indonesia", Region="Asia", Sales=3000 },
new Customer { ID="M", City="Tokyo", Country="Japan", Region="Asia", Sales=4000 },
new Customer { ID="N", City="Los Angeles", Country="USA", Region="North America", Sales=5000 },
new Customer { ID="O", City="Cairo", Country="Egypt", Region="Africa", Sales=6000 },
new Customer { ID="P", City="Tehran", Country="Iran", Region="Asia", Sales=7000 },
new Customer { ID="Q", City="London", Country="UK", Region="Europe", Sales=8000 },
new Customer { ID="R", City="Beijing", Country="China", Region="Asia", Sales=9000 },
new Customer { ID="S", City="Bogotá", Country="Colombia", Region="South America", Sales=1001 },
new Customer { ID="T", City="Lima", Country="Peru", Region="South America", Sales=2002 }
};
var queryResult1 = from c in customers where c.Region == "Asia"select c; //条件查询var queryResult2 = customers.Where(c => c.Region == "Asia");//lambda表达式,功能同1
//创建新对象var queryResult3 = from c in customers where c.Region == "North America"selectnew { c.City, c.Country, c.Sales };//创建新对象var queryResult4 = customers.Where(c => c.Region == "North America").
Select(c => new { c.City, c.Country, c.Sales });//lambda表达式，功能同3(注意此处调用顺序)
//Distinct()var queryResult5 = (from c in customers select c.Region).Distinct();//查找出不重复的地区var queryResult6 = customers.Select(c => c.Region).Distinct();//lambda表达式, 功能同5
//ALL和ANYbool anyUSA = customers.Any(c => c.Country == "USA");//是否存在USA的客户bool allAisa = customers.All(c => c.Region == "Asia");//是否全是Aisa客户
//多级排序var queryResult7 = from c in customers
orderby c.Region, c.Country, c.City
selectnew { c.ID, c.Region, c.Country, c.City };
//升降序(ThenBy和ThenByDescending在OrderBy之后)var queryResult8 = customers.OrderBy(c => c.Region).ThenByDescending(c => c.Country).
ThenBy(c => c.City).Select(c => new { c.ID, c.Region, c.Country, c.City });
//组合查询var queryResult9 = from c in customers group c by c.Region
into cg selectnew { TotalSales = cg.Sum(c => c.Sales), Regioin = cg.Key };
var queryResult10 = from cg in queryResult9 orderby cg.TotalSales descending select cg;//各区域消费总额排名
//Take() Skip()
queryResult9.Take(5);//前五
queryResult9.Skip(5);//跳过前五
//First() FirstOrDefault() queryResult9.First();
queryResult9.FirstOrDefault();
//集运算符
//Interserct();Except();Union();
//Joinvar queryResults =
from c in customers
join o in orders on c.ID equals o.ID
selectnew { c.ID, c.City, SalesBefore = c.Sales, NewOrder = o.Amount, SalesAfter = c.Sales + o.Amount };
}
}
}
LINQTOSQL:
using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Text;
namespace
Saku
{
class
Program
{
private
static DataClasses1DataContext dataContext = new DataClasses1DataContext();
publicstatic List<Teacher> stu = new List<Teacher>();
staticvoid Main(string[] args)
{
var queryResult = from c in dataContext.Teacher where c.tID == "0001"select c;
var queryResult1 = dataContext.Teacher.Where(c => c.tID == "0001");
foreach(var item in queryResult1)
{
Console.WriteLine(item.tName);
}
}
static Teacher Add(Teacher t)//增 {
dataContext.Teacher.InsertOnSubmit(t);
dataContext.SubmitChanges();
return t;
}
static Teacher Delete(Teacher t)//删除 {
dataContext.Teacher.DeleteOnSubmit(t);
dataContext.SubmitChanges();
return t;
}
staticvoid Show()//遍历 {
foreach (Teacher tch in dataContext.Teacher)
{
Console.WriteLine(tch.tID + "" + tch.tName + "" + tch.tPassword + "" + tch.tPhone + "" + tch.tAcademy + "" + tch.tDepartment + "" + tch.tRole);
}
}
staticbool Search(Teacher t)//查找 {
var queryResult = from n in dataContext.Teacher where n.tID == t.tID select n;
if(queryResult!=null)
{
Console.WriteLine("找到" + t.tID);
returntrue;
}
else
{
Console.WriteLine("没找到" + t.tID);
returnfalse;
}
}
staticvoid change()//改 {
var t = dataContext.Teacher.SingleOrDefault(c => c.tID == "0001");
t.tPhone = "13437196351";
dataContext.SubmitChanges();
}
}
}
未完待续。。
原文：http://www.cnblogs.com/Maskisland/p/5904513.html
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