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_Summary3 : 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" }; 
 
                // First - 返回集合中的第一个元素；不延迟 
                // FirstOrDefault - 返回集合中的第一个元素（如果没有则返回默认值）；不延迟 
                Summary_First_FirstOrDefault(); 
 
                // Last - 返回集合中的最后一个元素；不延迟 
                // LastOrDefault - 返回集合中的最后一个元素（如果没有则返回默认值） 
                Summary_Last_LastOrDefault(); 
 
                // ElementAt - 返回集合中指定索引的元素；不延迟 
                // ElementAtOrDefault - 返回集合中指定索引的元素（如果没有则返回默认值）；不延迟 
                Summary_ElementAt_ElementAtOrDefault(); 
 
                // Contains - 判断集合中是否包含有某一元素；不延迟 
                Summary_Contains(); 
 
                // Any - 判断集合中是否有元素满足某一条件；不延迟 
                Summary_Any(); 
 
                // All - 判断集合中是否所有元素都满足某一条件；不延迟 
                Summary_All(); 
 
                // Count - 返回集合中的元素个数，返回int；不延迟 
                // LongCount - 返回集合中的元素个数，返回long；不延迟 
                Summary_Count_LongCount(); 
 
                // Sum - 集合应为数字类型集合，求其和；不延迟 
                Summary_Sum(); 
 
                // Min - 返回集合的最小值；不延迟 
                Summary_Min(); 
 
                // Max - 返回集合的最大值；不延迟 
                Summary_Max(); 
 
                // Average - 集合应为数字类型集合，求其平均值；不延迟 
                Summary_Average(); 
 
                // Aggregate - 根据输入的表达式获取一个聚合值；不延迟 
                Summary_Aggregate(); 
 
                // Cast - 将集合转换为强类型集合；延迟 
                Summary_Cast(); 
 
                // DefaultIfEmpty - 查询结果为空则返回默认值；延迟 
                Summary_DefaultIfEmpty(); 
 
                // SequenceEqual - 判断两个集合是否相同；不延迟 
                Summary_SequenceEqual(); 
 
                // OfType - 过滤集合中的指定类型；延迟 
                Summary_OfType(); 
 
                // ToArray - 将集合转换为数组；不延迟 
                Summary_ToArray(); 
 
                // ToList - 将集合转换为List<T>集合；不延迟 
                Summary_ToList(); 
 
                // ToDictionary - 将集合转换为<K, V>集合；不延迟 
                Summary_ToDictionary(); 
        } 
}

/// <summary> 
        /// First - 返回集合中的第一个元素；不延迟 
        /// FirstOrDefault - 返回集合中的第一个元素（如果没有则返回默认值）；不延迟 
        /// </summary> 
        void Summary_First_FirstOrDefault() 
        { 
                string s = (from a in _ary 
                                        select a).First(a => a.StartsWith("s")); 
                // string s = (from a in _ary 
                //                         select a).FirstOrDefault(a => a.StartsWith("xxx")); 
                // s == null 
 
                result.InnerHtml += s + "<br />"; 
                result.InnerHtml += "<br />"; 
        }

/// <summary> 
        /// Last - 返回集合中的最后一个元素；不延迟 
        /// LastOrDefault - 返回集合中的最后一个元素（如果没有则返回默认值） 
        /// </summary> 
        void Summary_Last_LastOrDefault() 
        { 
                string s = (from a in _ary 
                                        select a).Last(a => a.StartsWith("s")); 
                // string s = (from a in _ary 
                //                         select a).LastOrDefault(a => a.StartsWith("sss")); 
                // s == null 
 
                result.InnerHtml += s + "<br />"; 
                result.InnerHtml += "<br />"; 
        }

/// <summary> 
        /// ElementAt - 返回集合中指定索引的元素；不延迟 
        /// ElementAtOrDefault - 返回集合中指定索引的元素（如果没有则返回默认值）；不延迟 
        /// </summary> 
        void Summary_ElementAt_ElementAtOrDefault() 
        { 
                string s = (from a in _ary 
                                        select a).ElementAt(3); 
                // string s = (from a in _ary 
                //                         select a).ElementAtOrDefault(1000); 
                // s == null 
 
                result.InnerHtml += s + "<br />"; 
                result.InnerHtml += "<br />"; 
        }

 /// <summary> 
        /// Contains - 判断集合中是否包含有某一元素；不延迟 
        /// </summary> 
        void Summary_Contains() 
        { 
                bool b = (from a in _ary 
                                    select a).Contains("javascript"); 
 
                result.InnerHtml += b.ToString() + "<br />"; 
                result.InnerHtml += "<br />"; 
        }

 /// <summary> 
        /// Any - 判断集合中是否有元素满足某一条件；不延迟 
        /// </summary> 
        void Summary_Any() 
        { 
                bool b = (from a in _ary 
                                    select a).Any(p => p.Length > 10); 
 
                result.InnerHtml += b.ToString() + "<br />"; 
                result.InnerHtml += "<br />"; 
        }

 /// <summary> 
        /// All - 判断集合中是否所有元素都满足某一条件；不延迟 
        /// </summary> 
        void Summary_All() 
        { 
                bool b = (from a in _ary 
                                    select a).All(p => p.Length > 10); 
 
                result.InnerHtml += b.ToString() + "<br />"; 
                result.InnerHtml += "<br />"; 
        }

/// <summary> 
        /// Count - 返回集合中的元素个数，返回int；不延迟 
        /// LongCount - 返回集合中的元素个数，返回long；不延迟 
        /// </summary> 
        void Summary_Count_LongCount() 
        { 
                int i = (from a in _ary 
                                 select a).Count(p => p.Length > 10); 
                // long i = (from a in _ary 
                //                     select a).LongCount(p => p.Length > 10); 
 
                result.InnerHtml += i.ToString() + "<br />"; 
                result.InnerHtml += "<br />"; 
        }