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。
代码语言：javascript复制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other1.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。
代码语言：javascript复制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other4.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other4.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other2.txt", FileMode.Open))
using (Stream outStream = new FileStream(@"f:.net学习other5.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other2.txt", FileMode.Open))
using (Stream outStream = new FileStream(@"f:.net学习other6.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。
代码语言：javascript复制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other6.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other7.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other7.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other7.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
代码语言：javascript复制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v
Dictionary<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。
