using System; 
using System.Data; 
using System.Configuration; 
using System.Collections; 
using System.Linq; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Web.UI.HtmlControls; 
using System.Xml.Linq; 
 
using System.Collections.Generic; 
using DAL; 
 
public partial class LINQ_Summary : System.Web.UI.Page 
{ 
        NorthwindDataContext _ctx = new NorthwindDataContext(); 
        string[] _ary = null; 
 
        protected void Page_Load(object sender, EventArgs e) 
        { 
                _ary = new string[] { "asp.net", "csharp", "xhtml", "css", "javascript",    
                        "wcf", "wpf", "silverlight", "linq", "wf",    
                        "sqlserver", "asp.net ajax", "ssis", "ssas", "ssrs" }; 
 
                // Select - Select选择；延迟 
                Summary_Select(); 
 
                // Where - Where查询；延迟 
                Summary_Where(); 
 
                // OrderBy - 按指定表达式对集合正序排序；延迟 
                // OrderByDescending - 按指定表达式对集合倒序排序；延迟 
                Summary_OrderBy_OrderByDescending(); 
 
                // GroupBy - 分组；延迟 
                Summary_GroupBy(); 
 
                // Join - Join查询；延迟 
                Summary_Join(); 
 
                // GroupJoin - 分组Join查询；延迟 
                Summary_GroupJoin(); 
        } 
}

/// <summary> 
        /// Select - Select选择；延迟 
        /// </summary> 
        void Summary_Select() 
        { 
                // 使用Select查询操作符 
                var categories = _ctx.Categories.Select( 
                        c => new { CategoryName = "类别名称：" + c.CategoryName }); 
 
                foreach (var c in categories) 
                { 
                        result.InnerHtml += c.CategoryName + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
 
 
                // 与上面的Select查询操作符相对应的查询语法 
                var categories2 = from c in _ctx.Categories 
                                                    select new { CategoryName = "类别名称：" + c.CategoryName }; 
 
                foreach (var c in categories2) 
                { 
                        result.InnerHtml += c.CategoryName + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
        }

/// <summary> 
        /// Where - Where查询；延迟 
        /// </summary> 
        void Summary_Where() 
        { 
                // 使用Where查询操作符 
                var ary = _ary.Where(a => a.StartsWith("w") && a.EndsWith("f")); 
 
                foreach (string s in ary) 
                { 
                        result.InnerHtml += s + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
 
 
                // 与上面的Where查询操作符相对应的查询语法 
                var ary2 = from a in _ary 
                                     where a.StartsWith("w") && a.EndsWith("f") 
                                     select a; 
 
                foreach (string s in ary2) 
                { 
                        result.InnerHtml += s + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
        }

 /// <summary> 
        /// OrderBy - 按指定表达式对集合正序排序；延迟 
        /// OrderByDescending - 按指定表达式对集合倒序排序；延迟 
        /// </summary> 
        void Summary_OrderBy_OrderByDescending() 
        { 
                // 使用OrderBy查询操作符 
                var ary = (from a in _ary 
                                     select a).OrderBy(a => a.Length); // OrderByDescending与OrderBy用法相同 
 
                foreach (string s in ary) 
                { 
                        result.InnerHtml += s + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
 
 
                // 与上面的OrderBy查询操作符相对应的查询语法 
                var ary2 = from a in _ary 
                                     orderby a.Length ascending // orderby xxx descending与orderby xxx ascending用法相同 
                                     select a; 
 
                foreach (string s in ary2) 
                { 
                        result.InnerHtml += s + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
        }

/// <summary> 
        /// GroupBy - 分组；延迟 
        /// </summary> 
        void Summary_GroupBy() 
        { 
                // 使用GroupBy查询操作符 
                var list = (from a in _ary 
                                        select a).GroupBy(a => a.Length).Select( 
                                                g => new { Group = g.Key, Member = g }); 
 
                foreach (var g in list) 
                { 
                        result.InnerHtml += g.Group + "个字符：<br />"; 
 
                        foreach (string s in g.Member) 
                        { 
                                result.InnerHtml += "--" + s + "<br />"; 
                        } 
                } 
                result.InnerHtml += "<br />"; 
 
 
                // 与上面的GroupBy查询操作符相对应的查询语法 
                var list2 = from a in _ary 
                                        group a by a.Length into g 
                                        select new { Group = g.Key, Member = g }; 
 
                foreach (var g in list2) 
                { 
                        result.InnerHtml += g.Group + "个字符：<br />"; 
 
                        foreach (string s in g.Member) 
                        { 
                                result.InnerHtml += "--" + s + "<br />"; 
                        } 
                } 
                result.InnerHtml += "<br />"; 
        }

/// <summary> 
        /// Join - Join查询；延迟 
        /// </summary> 
        void Summary_Join() 
        { 
                // 使用Join查询操作符 
                var products = _ctx.Products.Join( 
                        _ctx.Categories,    
                        p => p.CategoryID,    
                        c => c.CategoryID,    
                        (p, c) => new { c.CategoryName, p.ProductName }).Take(5); 
 
                foreach (var p in products) 
                { 
                        result.InnerHtml += p.CategoryName + " - " + p.ProductName + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
 
 
                // 与上面的Join查询操作符相对应的查询语法 
                var products2 = (from p in _ctx.Products 
                                                 join c in _ctx.Categories 
                                                 on p.CategoryID equals c.CategoryID 
                                                 select new { c.CategoryName, p.ProductName }).Take(5); 
 
                foreach (var p in products2) 
                { 
                        result.InnerHtml += p.CategoryName + " - " + p.ProductName + "<br />"; 
                } 
                result.InnerHtml += "<br />"; 
        }

 /// <summary> 
        /// GroupJoin - 分组Join查询；延迟 
        /// </summary> 
        void Summary_GroupJoin() 
        { 
                // 使用GroupJoin查询操作符 
                var products = _ctx.Categories.GroupJoin( 
                        _ctx.Products,    
                        c => c.CategoryID,    
                        p => p.CategoryID,    
                        (p, g) => new { p.CategoryName, ProductCount = g.Count() }); 
 
                foreach (var g in products) 
                { 
                        result.InnerHtml += g.CategoryName + "：" + g.ProductCount + "<br />"; 
 
                } 
                result.InnerHtml += "<br />"; 
 
 
                // 与上面的GroupJoin查询操作符相对应的查询语法 
                var products2 = from c in _ctx.Categories 
                                                join p in _ctx.Products on c.CategoryID equals p.CategoryID into g 
                                                select new { CategoryName = c.CategoryName, ProductCount = g.Count() }; 
 
 
                foreach (var g in products2) 
                { 
                        result.InnerHtml += g.CategoryName + "：" + g.ProductCount + "<br />"; 
 
                } 
                result.InnerHtml += "<br />"; 
        }