基本語法
var result=from item in container orderby value ascending/descending? ? ? ? ? ? ? ? ? select item;
1、獲取全部記錄
var allCars = from c in myCars select c;
(提取指定行記錄)
var allCars = (from c in myCars select c).Take<myCars>(5);//提取前5個數(shù)據(jù)
(模糊查詢)
var quest = from qu in mdc.Question where qu.Question1.Contains("數(shù)") selectqu;//模糊查詢
--------qu.Question1.Contains("數(shù)")//Linq的表的哪列的Contains()的方法
(Linq通過對象向數(shù)據(jù)庫添加數(shù)據(jù))
?
NewsInfo newnf = newNewsInfo(); ? ? ? ? ? newnf.newscontext =nf.newscontext; ? ? ? ? ? newnf.newsauthor =nf.newsauthor; ? ? ? ? ? newnf.newstime =DateTime.Now;//得到系統(tǒng)時間 ? ? ? ? ? mdc.NewsInfo.InsertOnSubmit(newnf);//標記添加狀態(tài) ? ? ? ? ? mdc.SubmitChanges();//執(zhí)行添加
2、只獲取字段名稱
var names = from c in myCars select c.PetName;//這里names就是隱式類型的變量。
3、使用Enumerable.Distinct<T>()
var makes = (from c in myCars select c.Make).Distinct<string>();
4、即可以在定義的時候調用Enumberalbe擴展函數(shù)
var names = from c in myCars select c.PetName;
foreach (var n in names)
{
Console.WriteLine("Name: {0}", n);
}
也可以在兼容的數(shù)組類型上調用
var makes = from c in myCars select c.Make;
Console.WriteLine("Distinct makes:");
foreach (var m in makes.Distinct<string>())
{
Console.WriteLine("Make: {0}", m);
}
var onlyBMWs = from c in myCars where c.Make == "BMW" selectc;
var onlyFastBMWs = from c in myCars
where c.Make == "BMW" && c.Speed >= 100 select c;
5、生成新的數(shù)據(jù)類型（投影）
var makesColors = from c in myCars select new {c.Make, c.Color};
6、Reverse<T>()
var subset = (from c in myCars select c).Reverse<Car>();
foreach (Car c in subset)
{
Console.WriteLine("{0} is going {1} MPH", c.PetName,c.Speed);
}或者
var subset = from c in myCars select c;
foreach (Car c in subset.Reverse<Car>())
{
Console.WriteLine(c.ToString());
}7、排序
默認是ascending
var subset = from c in myCars orderby c.PetName select c; subset = from c in myCars where c.Speed > 55 orderby c.PetName descending select c;
默認順序時也可以明確指明
var subset = from c in myCars orderby c.PetName ascending select c;
8、Enumerable.Except()
兩個IEnumerable<T>兼容的對象的差集
static void GetDiff()
{
List<string> myCars = new List<String>
{ "Yugo", "Aztec", "BMW"};
List<string> yourCars = new List<String>
{ "BMW", "Saab", "Aztec" };
var carDiff =(from c in myCars select c)
.Except(from c2 in yourCars select c2);
Console.WriteLine("Here is what you don't have, but I do:");
foreach (string s in carDiff)
Console.WriteLine(s);
}
? ? ? /// <summary>
? ? ? /// 添加一挑新聞
? ? ? /// </summary>
? ? ? /// <paramname="news"></param>
? ? ? public void AddNews(Newsnews) {
? ? ? ? ? gameLinq.News.InsertOnSubmit(news);
? ? ? ? ? gameLinq.SubmitChanges();
? ? ? }
? ? ? /// <summary>
? ? ? /// 根據(jù)ID刪除一天新聞
? ? ? /// </summary>
? ? ? /// <paramname="id"></param>
? ? ? public void DeleteNews(intid) {
? ? ? ? ? var news = from p ingameLinq.News where p.NewsId == id select p;
? ? ? ? ? gameLinq.News.DeleteAllOnSubmit(news);
? ? ? ? ? gameLinq.SubmitChanges();
? ? ? }
? ? ? /// <summary>
? ? ? /// 更新一天新聞
? ? ? /// </summary>
? ? ? /// <paramname="n"></param>
? ? ? public voidUpdateNews(News n) {
? ? ? ? ? var news = from p ingameLinq.News where p.NewsId == n.NewsId select p;
? ? ? ? ? News va =news.First();
? ? ? ? ? va.Content =n.Content;
? ? ? ? ? va.NewsState =n.NewsState;
? ? ? ? ? va.NewsTime =n.NewsTime;
? ? ? ? ? va.Title = n.Title;
? ? ? ? ? gameLinq.SubmitChanges();
? ? ? }
?
? ? ? /// <summary>
? ? ? /// 得到一個對象
? ? ? /// </summary>
? ? public UserInfoGetUserByUserid(string userid)
? ? ? {
? ? ? ? ? var u=from p inMyOfficeLinq.UserInfo where p.UserId==userid select p;
? ? ? ? ? UserInfouser=u.First();
? ? ? ? ? return user;
? ? ? }
? ? ?
? ? ? ///<summary>
? ? ? /// 得到所以對象集合
? ? ? /// </summary>
? ? ? ? publicList<RoleRight> GetAllRoleRight()
? ? ? ? {
? ? ? ? ? ? List<RoleRight>list = new List<RoleRight>();
? ? ? ? ? ? var r = from p inMyOfficeLinq.RoleRight select p;
? ? ? ? ? ? foreach (RoleRightitem in r)
? ? ? ? ? ? {
? ? ? ? ? ? ? ? list.Add(item);
? ? ? ? ? ? }
? ? ? ? ? ? return list;
? ? ? ? }
