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blog名称:乱闪Blog
日志总数:267
评论数量:1617
留言数量:-26
访问次数:2419614
建立时间:2005年1月1日 |
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 C# 2.0新特性探究之模拟泛型和内置算法
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在C#2.0中，匿名方法、IEnumerable接口和匿名方法的合作，使很多的编程任务变得非常的简单，而且写出来的程序非常的优美。
比如，我们可以写出如下的代码：
List＜Book＞ thelib = Library.getbooks();
List＜Book＞ found = thelib.FindAll(delegate(Book curbook)
{
if (curbook.isbn.StartsWith("..."))
return true;
return false;
});
foreach (Book b in found)
Console.WriteLine(b.isbn);
这段程序非常简单的展示给我们需要查找的信息，代码也非常的直接易懂。内置的数据结构给了我们强大的算法支持，不过，能不能够为自定义的类定义类似的算法呢？
比如，如果我有一个自定义的Library类并没有使用List＜Book＞存储数据，而是使用某种自定义的数据结构，我能不能也让用户使用类似的语法，忽略存储细节的使用匿名委托来实现特定的算法呢？
答案当然是肯定的，而且在C#中实现这样的功能是非常的简单。
首先让我们看看FindAll中用到的匿名委托的原型
public delegate bool Predicate＜T＞(T obj);
很明显的，上面的代码等于注册了一个搜索的回调，而在List内部定义了某种遍历的机制，从而实现了一个漂亮的算法结构Closure。
看到了这些，我们就可以定义自己的算法结构了，首先，我定义了一个如下的类
public class MyVec＜T＞
{
public static MyVec＜T＞ operator +(MyVec＜T＞ a, T b)
{
a._list.Add(b);
return a;
}
public override string ToString()
{
StringBuilder builder = new StringBuilder();
foreach (T a in _list)
{
builder.Append(a.ToString());
builder.Append(",");
}
string ret = builder.Remove(builder.Length - 1, 1).ToString();
return ret;
}
public MyVec＜T＜＞findAll(Predicate＜T＞ act)
{
MyVec＜T：＞t2 = new MyVec＜T＞();
foreach(T i in _list)
{
if (act(i))
t2._list.Add(i);
}
return t2;
}
// this is the inner object
private List＜T＞ _list = new List＜T＞();
}
这个类中包含了一个的List＜T＞结构，主要是为了证实我们的想法是否可行，事实上，任何一个可以支持foreach遍历的结构都可以作为内置的数据存储对象，我们会在后面的例子中给出一个更加复杂的实现。
下面是用于测试这个实验类的代码：
static void Main(string[] args)
{
MyVec＜int＞ a = new MyVec＜int＞();
a += 12;
a += 15;
a += 32;
MyVec＜int＞ b = a.findAll(delegate(int x)
{
if (x ＜ 20) return true; return false;
}
);
Console.WriteLine("vection original");
Console.WriteLine(a.ToString());
Console.WriteLine("vection found");
Console.WriteLine(b.ToString());
Console.ReadLine();
}
编译，执行，程序输出：
vection original
12,15,32
vection found
32
和我们预期的完全相同。很明显的，List内部的算法与我们预期的基本相同。
Predicate＜T＞仅仅是为了仿照系统的实现而采用的一个委托，事实上可以使用自己定义的任何委托作为回调的函数体。
通过使用IEnumberable接口，可以实现对任意结构的遍历，从而对任何数据结构定义强大的算法支持。 |
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C#中用API实现MP3等音频文件的播放类
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C#没有提供播放MP3等音频文件的类，要编写播放MP3等音频文件程序，必须使用第三方控件或类。本文使用API函数mciSendString，编写一个播放MP3等音频文件的类。
具体源码如下：
一、使用API函数mciSendString构成的媒体播放类。
using System;
using System.Runtime.InteropServices;
using System.Text;
using System.IO ;
namespace clsMCIPlay
{
/// <summary>
/// clsMci 的摘要说明。
/// </summary>
public class clsMCI
{
public clsMCI()
{
//
// TODO: 在此处添加构造函数逻辑
//
}
//定义API函数使用的字符串变量
[MarshalAs(UnmanagedType.ByValTStr,SizeConst=260)]
private string Name = "" ;
[MarshalAs(UnmanagedType.ByValTStr,SizeConst=128)]
private string durLength = "" ;
[MarshalAs(UnmanagedType.LPTStr,SizeConst=128)]
private string TemStr ="";
int ilong;
//定义播放状态枚举变量
public enum State
{
mPlaying = 1,
mPuase = 2,
mStop = 3
};
//结构变量
public struct structMCI
{
public bool bMut;
public int iDur;
public int iPos;
public int iVol;
public int iBal;
public string iName;
public State state;
};
public structMCI mc =new structMCI() ;
//取得播放文件属性
public string FileName
{
get
{
return mc.iName;
}
set
{
//ASCIIEncoding asc = new ASCIIEncoding();
try
{
TemStr ="";
TemStr = TemStr.PadLeft(127,Convert.ToChar(" "));
Name = Name.PadLeft(260,Convert.ToChar(" ")) ;
mc.iName = value;
ilong = APIClass.GetShortPathName(mc.iName,Name, Name.Length);
Name = GetCurrPath(Name);
//Name = "open " + Convert.ToChar(34) + Name + Convert.ToChar(34) + " alias media";
Name = "open " + Convert.ToChar(34) + Name + Convert.ToChar(34) + " alias media";
ilong = APIClass.mciSendString("close all", TemStr, TemStr.Length , 0);
ilong = APIClass.mciSendString( Name, TemStr, TemStr.Length, 0);
ilong = APIClass.mciSendString("set media time format milliseconds", TemStr, TemStr.Length , 0);
mc.state = State.mStop;
}
catch
{
MessageBox.Show("出错错误!");
}
}
}
//播放
public void play()
{
TemStr = "";
TemStr = TemStr.PadLeft(127,Convert.ToChar(" "));
APIClass.mciSendString("play media", TemStr, TemStr.Length , 0);
mc.state = State.mPlaying ;
}
//停止
public void StopT()
{
TemStr = "";
TemStr = TemStr.PadLeft(128,Convert.ToChar(" "));
ilong = APIClass.mciSendString("close media", TemStr, 128, 0);
ilong = APIClass.mciSendString("close all", TemStr, 128, 0);
mc.state = State.mStop ;
}
public void Puase()
{
TemStr = "";
TemStr = TemStr.PadLeft(128,Convert.ToChar(" "));
ilong = APIClass.mciSendString("pause media", TemStr, TemStr.Length, 0);
mc.state = State.mPuase ;
}
private string GetCurrPath(string name)
{
if(name.Length <1) return "";
name = name.Trim();
name = name.Substring(0,name.Length-1);
return name;
}
//总时间
public int Duration
{
get
{
durLength = "";
durLength = durLength.PadLeft(128,Convert.ToChar(" ")) ;
APIClass.mciSendString("status media length", durLength, durLength.Length, 0);
durLength = durLength.Trim();
if(durLength == "") return 0;
return (int)(Convert.ToDouble(durLength) / 1000f);
}
}
//当前时间
public int CurrentPosition
{
get
{
durLength = "";
durLength = durLength.PadLeft(128,Convert.ToChar(" ")) ;
APIClass.mciSendString("status media position", durLength, durLength.Length, 0);
mc.iPos = (int)(Convert.ToDouble(durLength) / 1000f);
return mc.iPos;
}
}
}
public class APIClass
{
[DllImport("kernel32.dll", CharSet = CharSet.Auto)]
public static extern int GetShortPathName (
string lpszLongPath,
string shortFile,
int cchBuffer
);
[DllImport("winmm.dll", EntryPoint="mciSendString", CharSet = CharSet.Auto)]
public static extern int mciSendString (
string lpstrCommand,
string lpstrReturnString,
int uReturnLength,
int hwndCallback
);
}
}
二、用于测试媒体播放类的简单代码：
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;
using System.Text;
using System.IO ;
using clsMCIPlay;
namespace MCIPlay
{
/// <summary>
/// Form1 的摘要说明。
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.ComponentModel.IContainer components;
private System.Windows.Forms.Timer timer1;
private System.Windows.Forms.Button Play;
private System.Windows.Forms.Button Stop;
private System.Windows.Forms.Button Puase;
private System.Windows.Forms.Label PlayFileName;
private System.Windows.Forms.Label Duration;
private System.Windows.Forms.Label CurrentPosition;
private System.Windows.Forms.OpenFileDialog openFileDialog1;
private System.Windows.Forms.Button BrowserFile;
clsMCI mp = new clsMCI();
public Form1()
{
//
// Windows 窗体设计器支持所必需的
//
InitializeComponent();
//
// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
//
}
/// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
this.Play = new System.Windows.Forms.Button();
this.PlayFileName = new System.Windows.Forms.Label();
this.Duration = new System.Windows.Forms.Label();
this.Stop = new System.Windows.Forms.Button();
this.Puase = new System.Windows.Forms.Button();
this.CurrentPosition = new System.Windows.Forms.Label();
this.timer1 = new System.Windows.Forms.Timer(this.components);
this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();
this.BrowserFile = new System.Windows.Forms.Button();
this.SuspendLayout();
//
// Play
//
this.Play.Location = new System.Drawing.Point(102, 243);
this.Play.Name = "Play";
this.Play.Size = new System.Drawing.Size(78, 24);
this.Play.TabIndex = 0;
this.Play.Text = "Play";
this.Play.Click += new System.EventHandler(this.Play_Click);
//
// PlayFileName
//
this.PlayFileName.AutoSize = true;
this.PlayFileName.Location = new System.Drawing.Point(12, 15);
this.PlayFileName.Name = "PlayFileName";
this.PlayFileName.Size = new System.Drawing.Size(0, 17);
this.PlayFileName.TabIndex = 1;
//
// Duration
//
this.Duration.AutoSize = true;
this.Duration.Location = new System.Drawing.Point(15, 51);
this.Duration.Name = "Duration";
this.Duration.Size = new System.Drawing.Size(0, 17);
this.Duration.TabIndex = 2;
//
// Stop
//
this.Stop.Location = new System.Drawing.Point(282, 243);
this.Stop.Name = "Stop";
this.Stop.Size = new System.Drawing.Size(81, 24);
this.Stop.TabIndex = 3;
this.Stop.Text = "Stop";
this.Stop.Click += new System.EventHandler(this.Stop_Click);
//
// Puase
//
this.Puase.Location = new System.Drawing.Point(198, 243);
this.Puase.Name = "Puase";
this.Puase.Size = new System.Drawing.Size(72, 24);
this.Puase.TabIndex = 4;
this.Puase.Text = "Puase";
this.Puase.Click += new System.EventHandler(this.Puase_Click);
//
// CurrentPosition
//
this.CurrentPosition.AutoSize = true;
this.CurrentPosition.Location = new System.Drawing.Point(15, 87);
this.CurrentPosition.Name = "CurrentPosition";
this.CurrentPosition.Size = new System.Drawing.Size(0, 17);
this.CurrentPosition.TabIndex = 5;
//
// timer1
//
this.timer1.Enabled = true;
this.timer1.Interval = 1000;
this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
//
// BrowserFile
//
this.BrowserFile.Location = new System.Drawing.Point(312, 165);
this.BrowserFile.Name = "BrowserFile";
this.BrowserFile.Size = new System.Drawing.Size(87, 24);
this.BrowserFile.TabIndex = 6;
this.BrowserFile.Text = "SelectFile";
this.BrowserFile.Click += new System.EventHandler(this.BrowserFile_Click);
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(433, 287);
this.Controls.Add(this.BrowserFile);
this.Controls.Add(this.CurrentPosition);
this.Controls.Add(this.Puase);
this.Controls.Add(this.Stop);
this.Controls.Add(this.Duration);
this.Controls.Add(this.PlayFileName);
this.Controls.Add(this.Play);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
#endregion
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
//选择MP3文件播放
private void Play_Click(object sender, System.EventArgs e)
{
try
{
mp.play();
}
catch
{
MessageBox.Show("出错错误!");
}
}
//暂停播放
private void Puase_Click(object sender, System.EventArgs e)
{
try
{
mp.Puase();
}
catch
{
MessageBox.Show("出错错误!");
}
}
//停止播放
private void Stop_Click(object sender, System.EventArgs e)
{
try
{
mp.StopT();
}
catch
{
MessageBox.Show("出错错误!");
}
}
//每秒显示一次播放进度
private void timer1_Tick(object sender, System.EventArgs e)
{
CurrentPosition.Text = mp.CurrentPosition.ToString();
}
//浏览文件
private void BrowserFile_Click(object sender, System.EventArgs e)
{
try
{
openFileDialog1.Filter = "*.mp3|*.mp3";
openFileDialog1.FileName = "";
if(openFileDialog1.ShowDialog() == DialogResult.OK)
{
mp.FileName = openFileDialog1.FileName ;
PlayFileName.Text = openFileDialog1.FileName ;
Duration.Text = mp.Duration.ToString() ;
}
}
catch
{
MessageBox.Show("出错错误!");
}
}
}
}
本程序在.net 2003 、win XP SP1下编译通过。 |
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