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 個資料
(模糊查詢)
var quest = from qu in mdc.Question
where qu.Question1.Contains("數")
select qu;//模糊查詢
--------qu.Question1.Contains("數")//Linq 的表的哪列的 Contains()的方法
(Linq 通過物件向資料庫添加資料)
NewsInfo newnf = new NewsInfo();
newnf.newscontext = nf.newscontext;
newnf.newsauthor = nf.newsauthor;
newnf.newstime = DateTime.Now;//得到系統時間
mdc.NewsInfo.InsertOnSubmit(newnf);//標記添加狀態
mdc.SubmitChanges();//執行添加
2. 只獲取欄位名稱 var names = from c in myCars select c.PetName;這里 names 就是隱式型別的變數。
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呼叫 Enumberalbe 擴展函式 var names = from c in myCars select c.PetName;
foreach (var n in names)
{ Console.WriteLine("Name: {0}", n); }
也可以在兼容的陣列型別上呼叫
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" select c;
var onlyFastBMWs = from c in myCars
where c.Make == "BMW" && c.Speed >= 100 select c;
5. 生成新的資料型別（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>兼容的物件的差集
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>
/// <param name="news"></param>
public void AddNews(News news)
{
gameLinq.News.InsertOnSubmit(news);
gameLinq.SubmitChanges();
}
/// <summary>
/// 根據 ID 洗掉一天新聞
/// </summary>
/// <param name="id"></param>
public void DeleteNews(int id)
{
var news = from p in gameLinq.News
where p.NewsId == id select p;
gameLinq.News.DeleteAllOnSubmit(news);
gameLinq.SubmitChanges();
}
/// <summary>
/// 更新一天新聞
/// </summary>
/// <param name="n"></param>
public void UpdateNews(News n)
{
var news = from p in gameLinq.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>
/// 得到一個物件
/// </summary>
public UserInfo GetUserByUserid(string userid)
{
var u=from p in MyOfficeLinq.UserInfo
where p.UserId==userid select p;
UserInfo user=u.First();
return user;
}
/// <summary>
/// 得到所以物件集合
/// </summary>
public List<RoleRight> GetAllRoleRight()
{
List<RoleRight> list = new List<RoleRight>();
var r = from p in MyOfficeLinq.RoleRight select p;
foreach (RoleRight item in r)
{
list.Add(item);
}
return list;
}
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樓主這是寫了些撒呀?是提問是分享?算不算水貼uj5u.com熱心網友回復：
C#這種lambda寫法意義好像不大，因為實際應用中sql陳述句復雜度可能更高。轉載請註明出處，本文鏈接：https://www.uj5u.com/qianduan/17072.html
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