这节课，我们学习了Stream的相关内容。
首先是Stream的大体介绍：.NET Framework provides Files and directories classes. These classes provide methods and properties for creating, naming, manipulating, and deleting files and directories on your disk, or Network. And it provides extensive support for serialization to create a stream of data(variables and objects). The .NET Framework provides buffered and unbuffered streams, and classes for asynchronous I/O.
关于file和directory：
1. Classes provided for file and directory manipulation.
2. The classes you need are in the System.IO namespace.
3. File class: Represents a file on disk.
4. Directory class: Represents a directory (Windows folder).
继承此类的对象可以跨越应用程序域边界被引用，甚至被远程引用。远程调用时， 将产生一个远程对象在本地的透明代理，通过此代理来进行远程调用。 使用代理交换消息来跨应用程序域边界进行通讯的对象的基类。
Working with Directories：
1. The Directory class exposes static methods for creating, moving, and exploring directories.
2. All the methods of the Directory class are static; therefore, you can call them all without having an instance of the class.
3. The DirectoryInfo class is a similar class, but one that has nothing but instance members (i.e.,no static members at all).
4. The FileSystemInfo class has a number of properties and methods that provide information about a file or directory.
Creating a DirectoryInfo：
1. Object To explore a directory hierarchy, you need to instantiate a DirectoryInfo object.
2. The DirectoryInfo class provides methods for getting not just the names of contained files and directories, but also FileInfo and DirectoryInfo objects, allowing you to dive in to the hierarchical structure, extracting subdirectories and exploring these recursively.
Working with Files：
1. The DirectoryInfo object can also return a collection of all the files in each subdirectory found.
2. The DirectoryInfo.GetFiles( ) method returns an array of FileInfo objects, each of which describes a file in that directory.
3. The FileInfo and File objects relate to one another, much as DirectoryInfo and Directory do.
4. Like the methods of Directory, all the File methods are static.
5. Like DirectoryInfo, all the methods of FileInfo are instance methods.
然后我试着运用了一下DirectoryInfo▼
其中
1. 从环境变量"SystemRoot"中得到特定字符串的值
string theDirectory = Environment.GetEnvironmentVariable("SystemRoot");
2.得到目录字符串theDirectory的对象
dir DirectoryInfo dir = new DirectoryInfo(theDirectory );
3.得到dir目录对象的文件集合
FileInfo[] filesInDir = dir.GetFiles();
4.得到dir对象的子目录集合
DirectoryInfo[] directories = dir.GetDirectories();
Principal methods of the Directory class：
CreateDirectory() ：Creates all directories and subdirectories specified by its path parameter
GetCreationTime() ：Returns and sets the time the specified directory was created
GetDirectories() ：Gets named directories
GetLogicalDrives() ：Returns the names of all the logical drives in the form <drive>:
GetFiles() ：Returns the names of files matching a pattern
GetParent() ：Returns the parent directory for the specified path
Move() ：Moves a directory and its contents to a specified path
Principal methods and properties of the DirectoryInfo class：
Attributes： Inherits from FileSystemInfo; gets or sets the creation time of the current file
CreationTime： Inherits from FileSystemInfo; gets or sets the creation time of the current file
Exists： Public property Boolean value, which is true if the directory exists
Extension： Public property inherited from FileSystemInfo; that is, the file extension
FullName： Public property inherited from FileSystemInfo; that is, the full path of the file or directory
LastAccessTime： Public property inherited from FileSystemInfo; gets or sets the last access time
LastWriteTime： Public property inherited from FileSystemInfo; gets or sets the time when the current file or directory was last written to
Name： Public property name of this instance of DirectoryInfo
Parent： Public property parent directory of the specified directory
Root： Public property root portion of the path
Create()： Public method that creates a directory
CreateSubdirectory()： Public method that creates a subdirectory on the specified path
Delete() ： Public method that deletes a DirectoryInfo and its contents from the path
GetDirectories() ： Public method that returns a DirectoryInfo array with subdirectories
GetFiles() ：Public method that returns a list of files in the directory
GetFileSystemInfos() ：Public method that retrieves an array of FileSystemInfo objects
MoveTo() ：Public method that moves a DirectoryInfo and its contents to a new path
Refresh() ：Public method inherited from FileSystemInfo; refreshes the state of the object
Principal public static methods of the File class：
AppendText() ：Creates a StreamWriter that appends text to the specified file
Copy() ： Copies an existing file to a new file
Create() ：Creates a file in the specified path
CreateText() ：Creates a StreamWriter that writes a new text file to the specified file
Delete() ：Deletes the specified file
Exists() ：Returns true if the specified file exists
GetAttributes(), SetAttributes() ：Gets or sets the FileAttributes of the specified file
GetCreationTime(), SetCreationTime() ：Returns or sets the creation date and time of the file
GetLastAccessTime(), SetLastAccessTime() ：Returns or sets the last time the specified file was accessed
GetLastWriteTime(), SetLastWriteTime() ：Returns or sets the last time the specified file was written to
Move() ：Moves a file to a new location; can be used to rename a file
OpenRead() ：Public static method that opens a FileStream on the file
OpenWrite() ：Creates a read/write Stream on the specified path
Principal methods and properties of the FileInfo class：
Attributes() ：Inherits from FileSystemInfo; gets or sets the attributes of the current file
CreationTime ：Inherits from FileSystemInfo; gets or sets the creation time of the current file
Directory ：Public property that gets an instance of the parent directory
Exists ：Public property Boolean value that is true if the directory exists
Extension ：Public property inherited from FileSystemInfo; that is, the file extension
FullName ：Public property inherited from FileSystemInfo; that is, the full path of the file or directory
LastAccessTime ：Public property inherited from FileSystemInfo; gets or sets the last access time
LastWriteTime ：Public property inheritedfrom FileSystemInfo; gets or sets the time when the current file or directory was last written to
Length ：Public property that gets the size of the current file
Name ：Public property Name of this DirectoryInfo instance
AppendText() ：Public method that creates a StreamWriter that appends text to a file
CopyTo() ：Public method that copies an existing file to a new file
Create() ：Public method that creates a new file
Delete() ：Public method that permanently deletes a file
MoveTo() ：Public method to move a file to a new location; can be used to rename a file
Open() ：Public method that opens a file with various read/write and sharing privileges
OpenRead() ：Public method that creates a read-only FileStream
OpenText() ：Public method that creates a StreamReader that reads from an existing text file
OpenWrite() ：Public method that creates a write-only FileStream
其实感觉这四部分大部分的都差不多……只有少数的几个是不一样的。
之后我们学习了关于改变文件读写数据一类的，因为还有一堆presentation没做怕玩脱了把电脑玩坏了就没做。