泛型委托例子

Framework2.0新增定义
 表示定义一组条件并确定指定对象是否符合这些条件的方法。此委托由 Array 和 List 类的几种方法使用，用于在集合中搜索元素。
public delegate bool Predicate<T>(T obj);

 

例子

protected void Page_Load(object sender, EventArgs e){ //首先定义一个list<>泛型 List<String> listString = new List<String>(); //添加数据listString.Add("One"); listString.Add("Two"); listString.Add("Three"); listString.Add("Four"); //返回结果,GetStringUpper方法的第二参数就是Predicate<T>系统库自定的委托this.text2.Value = GetStringUpper(listString.ToArray(),ExistString);}//调用委托public String GetStringUpper<T>(T[] listString,Predicate<String> p){ foreach (T item in listString) { if (p(item)) return item.ToString(); } return null;}//定义委托的实现方法public bool ExistString(string c){ return c.Length <= 4 && c.Contains("w"); }//public partial class Test_Test : PageBase{ SystemInfo info = new SystemInfo(); public Test_Test() { this.IsCheckEmployee = false; } protected void Page_Load(object sender, EventArgs e) { List<Account> accounts = new List<Account>(); accounts.Add(new Account("Christian", 1500)); accounts.Add(new Account("Sharon", 2200)); accounts.Add(new Account("Katie", 1800)); decimal amount = Algorithm.Accumulate<Account, decimal>( accounts, delegate(Account a, decimal d) { return a.Balance + d; }); this.text2.Value = amount.ToString(); decimal amount2 = Algorithm.Accumulate<Account, decimal>(accounts, Algorithm.AccountAdder<decimal>); text2.Value = text2.Value + "|" + amount2.ToString(); } public String GetStringUpper<T>(T[] listString, System.Predicate<T> p) { foreach (T item in listString) { if (p(item)) return item.ToString(); } return null; } public bool ExistString(string c) { return c.Length <= 4 && c.Contains("w"); }}/// <summary>/// 账面类/// </summary>public class Account { 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; } }//委托类public static class Algorithm{ public delegate TSummary Action<TInput, TSummary>(TInput t, TSummary u); public static TSummary Accumulate<TInput, TSummary>(IEnumerable<TInput> coll,Action<TInput, TSummary> action) { TSummary sum = default(TSummary); foreach (TInput input in coll) { sum = action(input, sum); } return sum; } public static decimal AccountAdder<TSummary>(Account a, TSummary d) { return a.Balance + Convert.ToDecimal(d); }}