//
using System;
using System.WinForms; // 在beta2版本中为：System.Windows.Forms
using System.IO;
class Set {
private Object[] items;
public Set(Int32 numItems) {
items = new Object[numItems];
for (Int32 i = 0; i < numItems; i++)
items[i] = i;
}
// 定义 Feedback，类型为delegate
// (注意: 这个类型在Set类中是嵌套的)
public delegate void Feedback(
Object value, Int32 item, Int32 numItems);
public void ProcessItems(Feedback feedback) {
for (Int32 item = 0; item < items.Length; item++) {
if (feedback != null) {
// 一旦指定了回调，便调用它们
feedback(items[item], item + 1, items.Length);
}
}
}
}
class App {
[STAThreadAttribute]
static void Main() {
StaticCallbacks();
InstanceCallbacks();
}
static void StaticCallbacks() {
// 创建一个Set对象，其中有五个项目
Set setOfItems = new Set(5);
// 处理项目，feedback=null
setOfItems.ProcessItems(null);
Console.WriteLine();
// 处理项目，feedback=Console
setOfItems.ProcessItems(new Set.Feedback(App.FeedbackToConsole));
Console.WriteLine();
// 处理项目，feedback =MsgBox
setOfItems.ProcessItems(new Set.Feedback(App.FeedbackToMsgBox));
Console.WriteLine();
// 处理项目，feedback = console AND MsgBox
Set.Feedback fb = null;
fb += new Set.Feedback(App.FeedbackToConsole);
fb += new Set.Feedback(App.FeedbackToMsgBox);
setOfItems.ProcessItems(fb);
Console.WriteLine();
}
static void FeedbackToConsole(
Object value, Int32 item, Int32 numItems) {
Console.WriteLine("Processing item {0} of {1}: {2}.",
item, numItems, value);
}
static void FeedbackToMsgBox(
Object value, Int32 item, Int32 numItems) {
MessageBox.Show(String.Format("Processing item {0} of {1}: {2}.",
item, numItems, value));
}
static void InstanceCallbacks() {
//创建一个Set对象，其中有五个元素
Set setOfItems = new Set(5);
// 处理项目，feedback=File
App appobj = new App();
setOfItems.ProcessItems(new Set.Feedback(appobj.FeedbackToFile));
Console.WriteLine();
}
void FeedbackToFile(
Object value, Int32 item, Int32 numItems) {
StreamWriter sw = new StreamWriter("Status", true);
sw.WriteLine("Processing item {0} of {1}: {2}.",
item, numItems, value);
sw.Close();
}
}
// |