C#中关于泛型方法和泛型委托的示例代码

在C#中除了可以定义泛型类外，我们还可以定义泛型方法和泛型委托。

在泛型方法中，泛型类型用方法声明来定义。

代码如下：

#region Using directivesusing System;using System.Collections;using System.Collections.Generic;using System.Text;#endregionnamespace GenericMethodDemo{public static class Algorithm{// 1. no operators with generics//public static T Max<T>(T x, T y)//{//if (x > y)//return x;//else//return y;//}public static T Max<T>(T x, T y, Comparison<T> comparer){int result = comparer(x, y);return result > 0 ? x : y;}public static decimal AccumulateSimple(IEnumerable e){decimal sum = 0;foreach (Account a in e){sum += a.Balance;}return sum;}public static decimal Accumulate<T, U>(U coll)where U : IEnumerable<T>where T : IAccount{decimal sum = 0;foreach (T a in coll){sum += a.Balance;}return sum;}public static decimal Accumulate<TAccount>(IEnumerable<TAccount> coll)where TAccount : IAccount{decimal sum = 0;foreach (TAccount a in coll){sum += a.Balance;}return sum;}public delegate U Adder<T, U>(T t, U u);public static U Accumulate<T, U>(IEnumerable<T> coll, Adder<T, U> adder){U sum = default(U);foreach (T a in coll){sum = adder(a, sum);}return sum;}public static U AccumulateIf<T, U>(IEnumerable<T> coll, Adder<T, U> adder, Predicate<T> match){U sum = default(U);foreach (T a in coll){if (match(a)){sum = adder(a, sum);}}return sum;}}public class Account : IAccount{private string name;public string Name{get{return name;}}private decimal balance;public decimal Balance{get{return balance;}}public Account(string name, Decimal balance){this.name = name;this.balance = balance;}}class Program{static int Compare(int x, int y){if (x == y)return 0;else if (x < y)return -1;elsereturn 1;}static decimal AccountAdder(Account a, decimal d){return a.Balance + d;}static void Main(string[] args){int i = 3;int j = 4;int result = Algorithm.Max<int>(i, j, new Comparison<int>(Program.Compare));List<Account> accounts = new List<Account>();accounts.Add(new Account("Christian", 1500));accounts.Add(new Account("Sharon", 2200));accounts.Add(new Account("Katie", 1800));foreach (Account a in accounts){Console.WriteLine(a.Name);}decimal sum1 = Algorithm.AccumulateSimple(accounts);Console.WriteLine(sum1);decimal sum2 = Algorithm.Accumulate(accounts);Console.WriteLine("sum of all accounts {0}", Algorithm.Accumulate<Account>(accounts));decimal sum3 = Algorithm.Accumulate<Account, decimal>(accounts, new Algorithm.Adder<Account, decimal>(AccountAdder));Console.WriteLine(sum3);decimal sum3b = Algorithm.Accumulate<Account, decimal>(accounts, AccountAdder);Console.WriteLine("3b " + sum3b);decimal sum4 = Algorithm.Accumulate<Account, decimal>(accounts,delegate(Account a, decimal d) { return a.Balance + d; });Console.WriteLine(sum4);decimal sum5 = Algorithm.AccumulateIf<Account, decimal>(accounts, delegate(Account a, decimal d) { return a.Balance + d; },delegate(Account a) {return a.Balance > 1800 ? true : false; });Console.WriteLine(sum5);Console.ReadLine();}}}

 

注意：

在C#2.0中，where子句的一个重要限制是，它不能定义必须由泛型类型实现的运算符。

运算符不能在接口中定义。使用where子句，只能定义基类，接口和默认构造函数。