第十二章 泛型

1. 空接合运算符（??） : op1 ?? op2 === op1 == null ? op2 : op1    ( tip:string.empty<>null)
2. List<T>:

   namespace 泛型
   {
       class Program
       {
           static void Main(string[] args)
           {
               List<MyClass> list = new List<MyClass>();
               list.Add(new MyClass("a"));
               list.Add(new MyClass("b"));
   
               foreach (var item in list)
               {
                   item.ToString();
               }
   
               Console.ReadKey();
           }
       }
   
       public class MyClass
       {
           public string Str;
   
           public MyClass(string str)
           {
               this.Str = str;
           }
   
           public new void ToString()
           {
               Console.WriteLine(this.Str);
           }
       }
   }

3. 排序：

   namespace Bazinga
   {
       class Program
       {
           static void Main(string[] args)
           {
               List<Nerd> nerds = new List<Nerd>();
               nerds.Add(new Nerd("Sheldon", 187));
               nerds.Add(new Nerd("Leonard", 173));
               nerds.Add(new Nerd("Howard", 168));
               nerds.Add(new Nerd("Rajesh", 170));
   
               nerds.Sort();
   
               Console.WriteLine("默认按智商排序:");
               foreach (var nerd in nerds)
               {
                   Console.WriteLine(nerd.ToString());
               }
   
               nerds.Sort(new NerdsSortByName());
               Console.WriteLine("\n按名字排序：");
               foreach (var nerd in nerds)
               {
                   Console.WriteLine(nerd.ToString());
               }
   
               Console.ReadKey();
           }
       }
   
       public class Nerd : IComparable<Nerd>
       {
           public string Name { get; set; }
           public int IQ { get; set; }
   
           public Nerd(string name, int iq)
           {
               this.Name = name;
               this.IQ = iq;
           }
   
           public int CompareTo(Nerd other)
           {
               return other.IQ - this.IQ;
           }
   
           public override string ToString()
           {
               return string.Format("{0},IQ:{1}", this.Name, this.IQ);
           }
       }
   
       public class NerdsSortByName : IComparer<Nerd>
       {
           public int Compare(Nerd x, Nerd y)
           {
               return x.Name.CompareTo(y.Name);
           }
       }
   }

4. 字典：

   namespace Dictionary
   {
       class Program
       {
           static void Main(string[] args)
           {
               Dictionary<string, int> dic = new Dictionary<string, int>();
               dic.Add("Sheldon", 187);
               dic.Add("Leonard", 173);
               dic.Add("Howard", 168);
               dic.Add("Rajesh", 170);         
   
               foreach (var item in dic.Keys)
               {
                   Console.WriteLine(item);
               }
   
               foreach (var item in dic.Values)
               {
                   Console.WriteLine(item);
               }
   
               foreach (KeyValuePair<string, int> item in dic)
               {
                   Console.WriteLine("{0},IQ:{1}", item.Key, item.Value);
               }
               Console.ReadKey();
           }
       }
   }

5. 定义泛型类：

   namespace GenericClass
    {
        class Program
        {
            static void Main(string[] args)
            {
                MyGenericClass<string> _string = new MyGenericClass<string>("string");
                MyGenericClass<string> _string_null = new MyGenericClass<string>();
                MyGenericClass<int> _int = new MyGenericClass<int>(100);
                MyGenericClass<int> _int_null = new MyGenericClass<int>();
                MyGenericClass<object> _object = new MyGenericClass<object>("object");
                MyGenericClass<object> _object_null = new MyGenericClass<object>();
    
                Console.WriteLine(_string.ToString());
                Console.WriteLine(_string_null.ToString());
                Console.WriteLine(_int.ToString());
                Console.WriteLine(_int_null.ToString());
                Console.WriteLine(_object.ToString());
                Console.WriteLine(_object_null.ToString());
    
                Console.ReadKey();
            }
        }
    
        public class MyGenericClass<T>//where T : object
        {
            public T t { get; set; }
            public MyGenericClass()
            {
                this.t = default(T);
            }
            public MyGenericClass(T t)
            {
                this.t = t;
            }
            public override string ToString()
            {
                string str = (t==null) ? "null" : t.ToString();
                return typeof(T) + " " + str;
            }
        }
    }