C#基础05

Stream（流）

之前学过的File类一般只能用于处理较小的文件（它读取的文件时要全部读取完并且是存储在内存中之后再处理数据，这会造成数据处理非常慢），而Stream类在处理文件时则时读取一些就处理一些，这样占用 的内存资源等会小很多处理数据也会快很多，所以适合处理文件数据较大的文件。

Stream类的具体的简单使用：

创建继承自Stream类的FileStream类的对象，这种方法不是特别推荐，（Stream fs = new FileStream（）；更好）

其中对于上面的这种构造方法，第二个参数有Create，Append，Truncate，CreateNew。

using System;
using System.IO;
using System.Text;namespace day05test01
{/// <summary>/// Stream 类的简单使用/// </summary>class Program{static void Main(string[] args){FileStream fs = new FileStream(@"F:\.net学习\other\1.txt", FileMode.Append);byte[] bytes = Encoding.Default.GetBytes("你就是秀儿吧" + System.Environment.NewLine);fs.Write(bytes, 0, bytes.Length);byte[] bytes1 = Encoding.Default.GetBytes("真他娘是个天才" + System.Environment.NewLine);fs.Write(bytes1, 0, bytes.Length);fs.Close();Console.WriteLine("Hello World!");}}
}

FileStream资源的正确释放

fs.Dispose(); //关闭流，并且进行一些资源清理

using只能捕获异常并抛出，并不能处理异常，所以要处理异常需要使用catch 子句。

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;namespace day05test02
{class Program{/// <summary>/// 使用using 简化  自动调用Dispose方法（无论是否有异常抛出都可执行）/// </summary>/// <param name="args"></param>static void Main(string[] args){/*using (Class1 cs1 = new Class1()){cs1.Write(3);}*/using (FileStream fs = new FileStream(@"f:\.net学习\other\4.txt", FileMode.Create)){String s = "hhh";byte[] bys = Encoding.Default.GetBytes(s);fs.Write(bys, 0, bys.Length);}Console.WriteLine("Hello World!");}}
}

FileStream的读取字节流

using System;
using System.ComponentModel.DataAnnotations;
using System.IO;
using System.Text;namespace day05test03
{class Program{static void Main(string[] args){using (FileStream fs = new FileStream(@"f:\.net学习\other\4.txt", FileMode.OpenOrCreate)){byte[] bytes = new byte[4]; //每次读取四个字节int len;/*len = fs.Read(bytes, 0, bytes.Length);Console.WriteLine(len);*///判断是否读到了末尾while ((len = fs.Read(bytes, 0, bytes.Length)) > 0){Console.WriteLine(len);//String s = Encoding.Default.GetString(bytes);String s = Encoding.Default.GetString(bytes, 0, len);Console.WriteLine(s);}}}}
}

FileStream 实现文件拷贝

using System;
using System.Diagnostics;
using System.IO;namespace day05test04
{class Program{/// <summary>/// 使用fileStream 实现文件拷贝/// </summary>/// <param name="args"></param>static void Main(string[] args){Stopwatch sw = new Stopwatch();sw.Start();try{using (Stream inStream = new FileStream(@"f:\.net学习\other\2.txt", FileMode.Open))using (Stream outStream = new FileStream(@"f:\.net学习\other\5.txt", FileMode.Create)){byte[] bytes = new byte[100];   //通过改变每次读取的字节数可以改变拷贝速度int len;while ((len = inStream.Read(bytes, 0, bytes.Length)) > 0){outStream.Write(bytes, 0, len);}}}catch{Console.WriteLine("1");}finally{sw.Stop();Console.WriteLine(sw.ElapsedMilliseconds);Console.WriteLine("Hello World!");}}}
}

练习——封装copy方法

using System;
using System.IO;namespace day05test05
{/// <summary>/// copy 方法封装练习/// </summary>class Program{static void Main(string[] args){using (Stream inStream = new FileStream(@"f:\.net学习\other\2.txt", FileMode.Open))using (Stream outStream = new FileStream(@"f:\.net学习\other\6.txt", FileMode.Create)){Copy(inStream, outStream);}Console.WriteLine("Hello World!");}//构成重载public static void Copy(Stream inStream, Stream outStream){Copy(inStream, outStream, 1024*1024);}public static void Copy(Stream inStream , Stream outStream, int bufferSize){byte[] bytes = new byte[bufferSize];int len;while ((len = inStream.Read(bytes, 0, bytes.Length)) > 0){outStream.Write(bytes, 0, len);}}}
}

多态的了解

通过使用WebRequest，等体会多态 的好处。

using System;
using System.IO;
using System.Net;namespace day05test06
{class Program{/// <summary>///WebRequest 的了解 /// </summary>/// <param name="args"></param>static void Main(string[] args){WebRequest re = WebRequest.Create("https://dss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=226419046,487093019&fm=26&gp=0.jpg");using (WebResponse res = re.GetResponse())using (Stream inStream = res.GetResponseStream())using (Stream outStream = new FileStream(@"f:\.net学习\other\6.jpg", FileMode.Create)){Console.WriteLine(inStream.GetType());Copy(inStream, outStream);}Console.WriteLine("Hello World!");}public static void Copy(Stream inStream, Stream outStream){Copy(inStream, outStream, 1024 * 1024);}public static void Copy(Stream inStream, Stream outStream, int bufferSize){byte[] bytes = new byte[bufferSize];int len;while ((len = inStream.Read(bytes, 0, bytes.Length)) > 0){outStream.Write(bytes, 0, len);}}}
}

StreamReater 和StreamWriter类

using System;
using System.IO;
using System.Text;namespace day05test07
{class Program{/// <summary>/// Reader Writer 类的使用适用于读取处理字符流的/// </summary>/// <param name="args"></param>static void Main(string[] args){using (Stream outStream = new FileStream(@"f:\.net学习\other\7.txt", FileMode.Create))using (StreamWriter sw = new StreamWriter(outStream, Encoding.Default)){sw.Write("nihao!  giao");sw.WriteLine("sadsadsada");}Console.WriteLine("Hello World!");}}
}

StreamWriter 
{///StreamWriter	伪代码实现private Stream stream; private Encoding encoding; public StreamWriter(Stream stream, Encoding encoding){  this. stream= stream; this. encoding=encoding; }public void Write(string s){byte[] bytes=encoding. GetBytes(s);stream. Write(bytes,0, bytes. length);}
}

using System;
using System.IO;
using System.Text;namespace day05test07
{class Program{/// <summary>/// Reader Writer 类的使用适用于读取处理字符流的/// </summary>/// <param name="args"></param>static void Main(string[] args){/*using (Stream outStream = new FileStream(@"f:\.net学习\other\7.txt", FileMode.Create))using (StreamWriter sw = new StreamWriter(outStream, Encoding.Default)){sw.Write("nihao!  giao");sw.WriteLine("sadsadsada");}*/using (Stream inStream = new FileStream(@"f:\.net学习\other\7.txt", FileMode.Open))using (StreamReader reader = new StreamReader(inStream, Encoding.Default)){//全部读取所有数据，小文件使用//String s = reader.ReadToEnd();//整行读取String ss = reader.ReadLine();Console.WriteLine(ss);}Console.WriteLine("Hello World!");}}
}

关于编码的理解：

List （泛型）容器

using System;
using System.Collections.Generic;namespace day05test08
{class Program{/// <summary>/// 泛型容器，List/// </summary>/// <param name="args"></param>static void Main(string[] args){//list <想要存放的数据类型> = new list<>（）；List<int> list = new List<int>();list.Add(3);list.Add(2);list.Add(5);//可添加数组list.AddRange(new int[] { 333, 666, 9});//for 循环遍历for (int i = 0; i < list.Count; i++){int num = list[i];Console.WriteLine(num);}// toarray 方法转换成数组int [] nums = list.ToArray();   //根据当前的list的元素创建数组Console.WriteLine("Hello World!");}}
}

Dictionary （泛型）字典

using System;
using System.Collections.Generic;namespace day05test09
{/// <summary>/// dictionary 字典泛型/// </summary>class Program{static void Main(string[] args){//Dictionary<k,v> 根据k，查询vDictionary<String, int> dit = new Dictionary<string, int>();dit.Add("a", 1);dit.Add("b", 2);dit.Add("c", 1);     //查询的值可以相同，键一定是唯一的//dit.Add("a",3);   如果有一个键对应多个值，程序将会抛出异常//如果存在就覆盖，如果不在就创建下面这种方式dit["b"] = 3;       //会将上定义的值覆盖，查询时不会产生异常int a = dit["a"];Console.WriteLine(a);Console.WriteLine(dit["c"]);Console.WriteLine(dit.ContainsKey("e"));Console.WriteLine(dit.ContainsKey("a"));Console.WriteLine("Hello World!");}}
}

foreach 循环

using System;
using System.Collections.Generic;namespace day05test10
{class Program{/// <summary>/// foreach 增强型循环对于所有实现了IEumerable接口的对象都可以使用/// </summary>/// <param name="args"></param>static void Main(string[] args){int[] nums = { 1, 2, 3, 154 };foreach (int num in nums){Console.WriteLine(num);}Console.WriteLine("Hello World!");//字典的遍历，Dictionary<String, object> dict = new Dictionary<string, object>();dict["a"] = 12;dict["b"] = "asd";dict["c"] = false;foreach (KeyValuePair<String, object> kvp in dict){Console.WriteLine(kvp.Key + "=" + kvp.Value);}}}
}

查漏补缺：

c#中怎么导入其它自定义的命名空间

（在手动导入命名空间后，需要自己去添加引用），添加引用后还需要注意被引用类的访问级别，如果是私有的则可能不能引用。

附加链接