泛型委托Predicate

此委托返回一个bool值，该委托通常引用一个"判断条件函数"。

需要指出的是，判断条件一般为“外部的硬性条件”,比如“大于50”，而不是由数据自身指定，不如“查找数组中最大的元素就不适合”。

 

例子一：

class Program     {         bool IsGreaterThan50(int i)         {             if (i > 50)                 return true;             else                 return false;         }

 

        static void Main(string[] args)         {             Program p=new Program();

            List<int> lstInt = new List<int>();             lstInt.Add(50);             lstInt.Add(80);             lstInt.Add(90);

            Predicate<int> pred = p.IsGreaterThan50;                         int i = lstInt.Find(pred);                         // 找到匹配的第一个元素，此处为80             Console.WriteLine("大于50的第一个元素为{0}",i);

           

            List<int> all = lstInt.FindAll(pred);             for (int j = 0; j < all.Count(); j++)             {                 Console.WriteLine("大于50的数组中元素为{0}", all[j]);  // 找出所有匹配条件的             }

            Console.ReadLine();         }     }

 

例子二:

class Staff     {         private double salary;

        public double Salary         {             get { return salary; }             set { salary = value; }         }

        private string num;

        public string Num         {             get { return num; }             set { num = value; }         }

        public override string ToString()         {             return "Num......" + num + "......" + "......" + "Salary......" + salary;         }     }

 

class Program     {         bool IsSalaryGreaterThan5000(Staff s)         {             if (s.Salary > 5000)                 return true;             else                 return false;         }

        static void Main(string[] args)         {             Program p = new Program();

            List<Staff> allStaff = new List<Staff>             {                 new Staff{Num="001",Salary=9999.9},                 new Staff{Num="002",Salary=8991},                 new Staff{Num="003",Salary=10000.8},                 new Staff{Num="004",Salary=4999.99}             };

 

            Predicate<Staff> s = p.IsSalaryGreaterThan5000;

            Staff theFirstOne = allStaff.Find(s);             Console.WriteLine(theFirstOne);              // 找出第一个

           

            List<Staff> all = allStaff.FindAll(s);             for (int i = 0; i < all.Count(); i++)             {                 Console.WriteLine(all[i]);               // 找出所有满足条件的             }

            Console.ReadLine();         }     }