RegularExpressions 正規表示式檢查函式

正整數1-3位或正整數含1-2位小數的浮點數

^(([0-9]{1,3})([.][0-9]{1,2})?)$


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聰明的動態型別 dynamic

程式碼：

           
dynamic d = 1; //初始型別是數字
        
Console.WriteLine("d type :{0},d status:{1}", d.GetType(),d);
           
d += "test";  //故意加上文字（正常這裡vs2013編輯器就會顯示錯誤了）

Console.WriteLine("d type :{0},d status:{1}", d.GetType(), d);

Console.ReadKey();

結果：可以看到d初始型別是int32，加上文字後自動將型別轉成字串型別，沒有顯示任何錯誤

動態型別可以略過編輯時期檢查，還會自動改變型別真是太讚了！


更多內容可以參考此篇：

了解 C# 4 的動態關鍵字

[LinQ] Groupby 與 ToLookup 差異

成績類別：

    public class Grade {
        public string Name { get; set; }
        public int Value { get; set; }
        public string Group { get; set; }
    }                                                                                   

主程式：

            List<Grade> val= new List<Grade> { 
                new Grade{Name="alvin",Value=85,Group ="A"},
                new Grade{Name="lily",Value=75,Group="B"},
                new Grade{Name="john",Value=65,Group="C"},
                new Grade{Name="helen",Value=77,Group="B"},
                new Grade{Name="mary",Value=78,Group="B"},
                new Grade{Name="jack",Value=89,Group="A"},
            };


            var gok = val.GroupBy(c => c.Group);    //GroupBy還沒有將資料取回
            var lok = val.ToLookup(c => c.Group);    //此段已將資料取回

            val.RemoveAll(c => true );   //將原始資料清空

            Console.WriteLine("==========GroupBy start==========");
            foreach (var g in gok) {       
                Console.WriteLine("=====group:{0}=====", g.Key);
                foreach (var p in g) {
                    Console.WriteLine("name:{0},value:{1},group:{2}",p.Name  ,p.Value  ,p.Group  );
                }
            }
          
            
            Console.WriteLine("==========ToLookup start==========");
            foreach (var g in lok) {
                Console.WriteLine("=====group-{0}=====", g.Key);
                foreach (var p in g) {
                    Console.WriteLine("name:{0},value:{1},group:{2}",p.Name  ,p.Value ,p.Group   );
                }
            }    
            Console.ReadKey();

結果：Groupby沒有資料出現，因為Groupby時沒有立即將資料取回，所以後面Removeall後，再執行就沒資料可用

完整程式碼：

https://www.dropbox.com/s/72p8ayukwaauyun/20141205.txt?dl=0

結果：差別在立即將資料取回(ToLookup)和延遲取回資料(Groupby)

[委派] Console測試匿名委派

委派函式：

delegate void TestDelegate(string str);


程式碼：

       
static void Main(string[] args) {
     TestDelegate t1 = (string s1) => { Console.WriteLine("print from s1:" + s1); };
     TestDelegate t2 = (string s2) => { Console.WriteLine("print from s2:" + s2); };

     t1 += t1 + t2 + t1;
     t1("Hello");
     t1.Invoke("Hello world");
     Console.ReadKey();
}

結果：

更多內容可以參考：

Lambda 運算式 (C# 程式設計手冊)

各版本的Sql connection 字串寫法

LocalDB:

<add name="ConnectionStringName" providerName="System.Data.SqlClient"  
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFileName=|DataDirectory|\DatabaseFileName.mdf;InitialCatalog=DatabaseName;Integrated Security=True;MultipleActiveResultSets=True" />

Sql Express:

<add name="ConnectionStringName" providerName="System.Data.SqlClient"
    connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=DatabaseName;Integrated Security=True;MultipleActiveResultSets=True"/>

Sql Server:

<add name="ConnectionStringName" providerName="System.Data.SqlClient"
    connectionString="Data Source=ServerName;Initial Catalog=DatabaseName;Integrated Security=False;User Id=userid;Password=password;MultipleActiveResultSets=True" />                        

SQL Azure:

<add name="ConnectionStringName"  providerName="System.Data.SqlClient"
    connectionString="Data Source=tcp:ServerName.database.windows.net,1433;Initial Catalog=DatabaseName;Integrated Security=False;User Id=username@servername;Password=password;Encrypt=True;TrustServerCertificate=False;MultipleActiveResultSets=True" />

Entity Framework Database:

<add name="ConnectionStringName"  providerName="System.Data.EntityClient"
    connectionString="metadata=res://*/ ContextClass.csdl|res://*/ ContextClass.ssdl|res://*/ ContextClass.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=ServerName;Integrated Security=False;User Id=userid;Password=password;MultipleActiveResultSets=True&quot;" />

Sql Compact:

<add name="ConnectionStringName" providerName="System.Data.SqlServerCe.4.0"
    connectionString="Data Source=|DataDirectory|\DatabaseFileName.sdf" />