步步为营VS 2008 + .NET 3.5(5) - LINQ查询操作符之Select、Where、OrderBy、OrderByDescending

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 />"; 
        }