C# Path 有关于文件路径等问题类(转)
C# Path
Path handles file path processing. The .NET Framework provides effective ways of dealing with filenames and paths. It introduces the Path type in the System.IO namespace. There are complications when dealing directly with paths.
Example
You will often need to extract parts of filename paths in your programs. The .NET Framework team at Microsoft has thought of this problem—the Path class is ideal. You can access it by adding “using System.IO” at the top of your class.
Next: As an introduction, we see a short console program that shows four Path methods.
Program that uses Path methods: C# using System;
using System.IO; class Program
{
static void Main()
{
string path = "C:\\stagelist.txt"; string extension = Path.GetExtension(path);
string filename = Path.GetFileName(path);
string filenameNoExtension = Path.GetFileNameWithoutExtension(path);
string root = Path.GetPathRoot(path); Console.WriteLine("{0}\n{1}\n{2}\n{3}",
extension,
filename,
filenameNoExtension,
root);
}
} Output .txt
stagelist.txt
stagelist
C:\
In this example, we take the extension of the file, the actual filename, the filename without the extension, and the path root. The path root is “C:\\”, with the trailing separator, even when the file is nested in many folders.
GetFileName. You can get the filename alone by calling the Path.GetFileName method. This will return the filename at the end of the path, along with the extension, such as .doc or .exe.
Also: There is a method to just get the extension, and one just to get the name with no extension—Path.GetFileNameWithoutExtension.
Example 2
It is useful to see the results of the Path methods on various inputs. Sometimes the methods handle invalid characters as you might expect. Sometimes they do not. This program calls three Path methods on an array of possible inputs.
Program that tests Path class: C# using System;
using System.IO; class Program
{
static void Main()
{
string[] pages = new string[]
{
"cat.aspx",
"really-long-page.aspx",
"test.aspx",
"invalid-page",
"something-else.aspx",
"Content/Rat.aspx",
"http://dotnetperls.com/Cat/Mouse.aspx",
"C:\\Windows\\File.txt",
"C:\\Word-2007.docx"
};
foreach (string page in pages)
{
string name = Path.GetFileName(page);
string nameKey = Path.GetFileNameWithoutExtension(page);
string directory = Path.GetDirectoryName(page);
// // Display the Path strings we extracted. //
Console.WriteLine("{0}, {1}, {2}, {3}",
page, name, nameKey, directory);
}
}
} Output: reformatted Input: cat.aspx
GetFileName: cat.aspx
GetFileNameWithoutExtension: cat
GetDirectoryName: - Input: really-long-page.aspx
GetFileName: really-long-page.aspx
GetFileNameWithoutExtension: really-long-page
GetDirectoryName: - Input: test.aspx
GetFileName: test.aspx
GetFileNameWithoutExtension: test
GetDirectoryName: - Input: invalid-page
GetFileName: invalid-page
GetFileNameWithoutExtension: invalid-page
GetDirectoryName: - Input: Content/Rat.aspx
GetFileName: Rat.aspx
GetFileNameWithoutExtension: Rat
GetDirectoryName: Content Input: http://dotnetperls.com/Cat/Mouse.aspx
GetFileName: Mouse.aspx
GetFileNameWithoutExtension: Mouse
GetDirectoryName: http:\dotnetperls.com\Cat Input: C:\Windows\File.txt
GetFileName: File.txt
GetFileNameWithoutExtension: File
GetDirectoryName: C:\Windows Input: C:\Word-2007.docx
GetFileName: Word-2007.docx
GetFileNameWithoutExtension: Word-2007
GetDirectoryName: C:\
Extensions. GetFileNameWithoutExtension will return the entire file name if there’s no extension on the file.Path.GetDirectoryName returns the entire string except the file name and the slash before it.
Path methods and URLs. Please look at the table above where the directory name of the URL is received. The slashes are reversed into Windows-style slashes. This is not desirable with virtual paths or URLs.
Tip: The volume such as “C:\” is part of the directory name. The directory name doesn’t include the trailing slash “\”.
Syntax
When specifying paths in C# programs, we must use two backslashes “\\” unless we use the verbatim string syntax. A verbatim string uses the prefix character “@”. Only one backslash is needed in this literal syntax.
Program that uses verbatim string: C# using System;
using System.IO; class Program
{
static void Main()
{
// ... Verbatim string syntax.
string value = @"C:\directory\word.txt";
Console.WriteLine(Path.GetFileName(value));
}
} Output word.txt
Extensions
The Path type includes also support for extensions. We can get an extension, with GetExtension, or even change an extension with ChangeExtension. The method names are obvious and easy-to-remember.
GetExtension handles extensions of four letters. It also handles the case where a file name has more than one period in it. This next program briefly tests GetExtension. You can find further details and benchmarks.
Path.GetExtension Path.ChangeExtension
Program that uses GetExtension: C# using System;
using System.IO; class Program
{
static void Main()
{
// ... Path values.
string value1 = @"C:\perls\word.txt";
string value2 = @"C:\file.excel.dots.xlsx"; // ... Get extensions.
string ext1 = Path.GetExtension(value1);
string ext2 = Path.GetExtension(value2);
Console.WriteLine(ext1);
Console.WriteLine(ext2);
}
} Output .txt
.xlsx
Path.Combine
Path.Combine is a useful method, but there are edge cases it cannot solve. It can’t figure out what you want if what it receives is confusing. But different inputs can yield the same result path.
Next: Here’s a screenshot where we combine the folder “Content\\” with the file name “file.txt”.
The screenshot shows what values Path.Combine produced. It shows that the following two lines of code produce the same result. Path.Combine handles certain cases where you have directory separators in different positions.
Program that uses Path.Combine: C# using System; class Program
{
static void Main()
{
// // Combine two path parts. //
string path1 = System.IO.Path.Combine("Content", "file.txt");
Console.WriteLine(path1); // // Same as above but with a trailing separator. //
string path2 = System.IO.Path.Combine("Content\\", "file.txt");
Console.WriteLine(path2);
}
} Output Content\file.txt
Content\file.txt
The example above also shows how to refer the Path class by specifying “System.IO.Path” instead of including the namespace at the top of your file. This may be useful in source files that are not file-IO oriented.
Tip: When using a C-style language such as C# or C++, you have to add the char \ to your C# code, you must use \\ (two backslashes).
Note: That’s because C# uses the backslash to escape characters, so you must escape it.
ASP.NET paths
The Path class doesn’t work well for URLs or virtual paths, but it is still useful in ASP.NET websites. For each ASP.NET request, there is a Request.PhysicalPath. That value is Windows-style path—it works well with the Path class.
Code that tests extensions: C# // // This could be in your Global.asax file or in an ASPX page. // It gets the physical path. //
string physical = Request.PhysicalPath;
// // Here we see if we are handling an ASPX file. //
if (Path.GetExtension(physical) == ".aspx")
{
// // Get the file name without an extension. //
string key = Path.GetFileNameWithoutExtension(physical);
}
Random file names
Random file names are useful for many programs. If you need to write a temp file or log and you don’t care about the path, use Path.GetRandomFileName. You can use this for random strings, too, but that isn’t its primary purpose.
Tip: Here’s the random string it yielded just now: zd4xcjmo.u4p. No file of that name likely exists.
Separator characters
The Path type also includes two properties for separators. These are good for creating code that is easy to understand, as it is easier for some developers to read Path.DirectorySeparatorChar.
Next: I looked at these two properties in the debugger and the results are shown below.
Path.DirectorySeparatorChar result "\\" Path.AltDirectorySeparatorChar result "/"
Temporary file names
There exist methods for getting temporary file names. When looking at them in the debugger, they point to a “Temp” folder in your User folder. Here are what Visual Studio’s debugger says my temp file names equal.
Note: GetTempPath() has a separator character on the end, unlike Path.GetDirectoryName’s return value.
Path.GetTempFileName result C:\\Users\\allensamuel\\AppData\\Local\\Temp\\tmpC1D0.tmp
The output file name ends with ".tmp". Path.GetTempPath result C:\\Users\\allensamuel\\AppData\\Local\\Temp\\
The output path ends with the backslash character, \\.
Invalid characters
When accepting input from your user, your program should expect that invalid characters will be entered. For example, your program has a custom file name dialog. You need to quickly detect invalid path characters.
So: You can use the Path.GetInvalidFileNameChars and Path.GetInvalidPathChars methods.
Tip: You can use the character arrays returned by Path.GetInvalidFileNameChars and Path.GetInvalidPathChars with a Dictionary.
Program that gets invalid characters: C# using System;
using System.Collections.Generic;
using System.IO;
using System.Linq; class Program
{
static void Main()
{
// First, we build a Dictionary of invalid characters.
var dict = GetInvalidFileNameChars();
// Next, we test the dictionary to see if the asterisk (star) is valid.
if (dict.ContainsKey('*'))
{
// This will run, because the star is in the Dictionary.
Console.WriteLine("* is an invalid char");
}
} /// <summary> /// Get a Dictionary of the invalid file name characters. /// </summary>
static Dictionary<char, bool> GetInvalidFileNameChars()
{
// This method uses lambda expressions with ToDictionary.
return Path.GetInvalidFileNameChars().ToDictionary(c => c, c => true);
}
} Output * is an invalid char
Discussion
Path is a powerful class. It can change a file name’s extension. It can determine whether the path is “rooted”—meaning whether it is relative or absolute. You can also get information about the volume, which is usually your hard drive.
Tip: Getting the directory name of your string path is often useful. There are also benchmarks of Path.GetDirectoryName.
We should remember that Path is best used only for certain types of paths. Web addresses are considered paths, but in the .NET Framework they are URIs. And the Uri type—described further down on this page—is best for them.
Warning: I suggest that you don’t use Path for URLs or virtual paths in ASP.NET. The Path type has inconsistencies with directory names.
Also: It doesn’t have lookup tables for invalid characters, so you need to use the array or a Dictionary, such as the one we saw here.
File lists
It is a common requirement to need to get lists of files in certain directories. Also, we show how to get recursive lists of files, by traversing subdirectories. These are not Path methods but they do return path strings.
Directory.GetFiles, Get File List Recursive File List
Misc.
Some custom methods may be helpful when working with the Path class. For example, storing a list of reserved filenames and then testing to see if a filename is reserved can improve certain programs.
Path Exists Reserved Filenames
Optimization: There are ways to optimize the Path methods so that they are more efficient.
But: You must be careful not to change the functionality in ways that are detrimental.
Uri
The Uri type provides support for website addresses and paths. It contains many helper methods you can use to specify addresses of websites. If a path starts with http, it is a better idea to use Uri.
Summary
We used Path for Windows-native path manipulations and tests, in the C# language. It is ideal for file names, directory names, relative paths, file name extensions, and invalid character testing.
Thus: These examples hopefully put you on the path to good file path handling in the .NET Framework.
出自:http://www.dotnetperls.com/path
C# Path 有关于文件路径等问题类(转)的更多相关文章
- C# Path 有关于文件路径获取的问题 的方法
string Current = Directory.GetCurrentDirectory();//获取当前根目录 //private string strFilePath = Applicatio ...
- Android根据文件路径使用File类获取文件相关信息
Android通过文件路径如何得到文件相关信息,如 文件名称,文件大小,创建时间,文件的相对路径,文件的绝对路径等: 如图: 代码: public class MainActivity extends ...
- android--------根据文件路径使用File类获取文件相关信息
Android通过文件路径如何得到文件相关信息,如 文件名称,文件大小,创建时间,文件的相对路径,文件的绝对路径等. 如图: public class MainActivity extends Act ...
- python 文件路径操作方法(转)
Python编程语言在实际使用中可以帮助我们轻松的实现一些特殊的功能需求.在这里我们将会为大家详细介绍一下有关Python文件路径的相关操作技巧,从而方便我们在实际开发中获得一些帮助. Python文 ...
- Mac automator bash 自动操作 右键菜单unrar解压 拷贝文件路径到剪贴板 快速删除(rm -rf) 快捷键设置
https://tecadmin.net/pass-command-line-arguments-in-shell-script/ https://tecadmin.net/tutorial/bash ...
- [LeetCode] Longest Absolute File Path 最长的绝对文件路径
Suppose we abstract our file system by a string in the following manner: The string "dir\n\tsub ...
- nginx之七:nginx path(root)文件路径配置
nginx指定文件路径有两种方式root和alias,这两者的用法区别,使用方法总结了如下,方便大家在应用过程中,快速响应.root和alias主要区别在于如何解释location后面的uri,这会使 ...
- Linux 中C/C++ search path(头文件搜索路径)
https://blog.csdn.net/BjarneCpp/article/details/76135980 起因 我拿到了一套Linux下的C++代码,代码中有这个头文件#include < ...
- [LeetCode] Simplify Path,文件路径简化,用栈来做
Given an absolute path for a file (Unix-style), simplify it. For example,path = "/home/", ...
随机推荐
- unity3d 各键值对应代码
KeyCode :KeyCode是由Event.keyCode返回的.这些直接映射到键盘上的物理键. 值 对应键 Backspace 退格键 Delete Delet ...
- Mac OS 小知识
删除Mac OS输入法中自动记忆的用户词组 有时候不小心制造了一个错误的词组,结果也被输入法牢牢记住,这时候可以用shift+delete组合键来删除 快捷键拾遗 Fn+Delet ...
- SpringMVC(四)@RequestParam
使用@RequestParam可以将URL中的请求参数,绑定到方法的入参上,并通过@RequestParam的3个参数进行配置 Modifier and Type Optional Element D ...
- 关于在win7旗舰版32位上 安装 net4.0 的闪退问题研究 和安装sqlserver2008问题
1.配置文件客户端[目标x86x64]的 可以安装 2.配置文件完全的目标x86x64的 出现闪退. 3.服务器核心的出现无法安装 安装 sqlserver 2008R2数据库 报错 \最后留下了它, ...
- C#---EF映射MySQL
使用EF CodeFirst连接MySql数据库 如何使用EF CodeFirst连接MySql数据库? 我们这篇文章介绍怎么使用EF连接MySql 作者的环境 VS2017.Win10.MySql5 ...
- 基于fpga的256m的SDRAM控制器
2018/7/26 受教于邓堪文老师,开始真真学习控制sdram 由于自己买的sdram模块是256的,原来老师的是128,所以边学边改,不知道最后好不好使,但是我有信心 一.sdram的初始化 sd ...
- kernel memory code learn
mem alloc page Noticeble: 1. there are two kind of page: virtual page, physical page. 2. the page st ...
- uva 540 (Team Queue UVA - 540)
又是一道比较复杂的模拟题.题中有两种队列,一种是总队列,从前向后.其他的是各个团体的小队列,因为入队的人如果有队友的话,会优先进入团体队列. 所以我们先设置两个队列和一个map,设置map倒是可以不用 ...
- [pytorch学习]1.pytorch ubuntu安装
看完了Deep Learning with Python,尝试了部分Keras的demo代码. 感觉Keras虽然容易上手,能够快速搭建出一个通用的模型,但是缺乏对底层的控制. 同时,在使用了自己编译 ...
- STM32学习笔记:读写内部Flash(介绍+附代码)
一.介绍 首先我们需要了解一个内存映射: stm32的flash地址起始于0x0800 0000,结束地址是0x0800 0000加上芯片实际的flash大小,不同的芯片flash大小不同. RAM起 ...