100165427.htm
来自「C#高级编程(第三版),顶死你们。。 。up」· HTM 代码 · 共 103 行
HTM
103 行
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>
14.2.4 拒绝权限
</title></head>
<body>
<div class="area">
<div class="col1">
<div class="lineBlue">
</div>
<!-- title -->
<div class="arcTitle">
<h1>
<a href="../16">
C#高级编程（第3版）【全文连载】
</a>
</h1>
<div style="text-align: center; font-size: 15px">
<a href="100165427.htm">
14.2.4 拒绝权限
</a>
</div>
<div style="text-align: center; font-size: 15px">
<a class="url" href="../../default.htm">http://book.csdn.net/</a>
2006-10-13 14:41:00
</div>
<div style="margin: 0px auto; width: 700px; border: solid 1px #0b5f98;">
<div style="float: left; width: 16px; background-color: #0b5f98; color: White; padding: 1px;">
图书导读
</div>
<div style="float: right; width: 670px; text-align: left; line-height: 16pt; padding-left: 2px">
<!--导读-->
<h1 id="divCurrentNode" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165427.htm'><font color='red'>14.2.4 拒绝权限</font></a></h1>
<div id="divRelateNode" style="padding-left: 2px">
<div style='float:left;width:49%'>·<a href='100165424.htm'>14.2.1 要求权限</a></div><div style='float:right;width:49%'>·<a href='100165425.htm'>14.2.2 请求权限</a></div><div style='float:left;width:49%'>·<a href='100165426.htm'>14.2.3 隐式的权限</a></div><div style='float:right;width:49%'>·<a href='100165428.htm'>14.2.5 断言权限</a></div><div style='float:left;width:49%'>·<a href='100165429.htm'>14.2.6 创建代码访问权限</a></div><div style='float:right;width:49%'>·<a href='100165430.htm'>14.2.7 声明的安全性</a></div></div>
</div>
</div>
</div>
<!-- main -->
<div id="main">
<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 8.15pt"><a ftel="_Toc507815607"><span lang="EN-US">14.2.4 </span></a><span style="FONT-FAMILY: 黑体">拒绝权限</span></h3>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">有些情况下，需要执行一项操作，并绝对确保所调用的方法在一个受保护的环境中执行。例如，在调用第三方的类时，要确保它不会访问本地磁盘。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">为此，可以创建一个权限的实例，并确保没有给它授予</span><span lang="EN-US">Deny()</span><span style="FONT-FAMILY: 宋体">方法，然后，在调用权限类之前，首先调用权限类的</span><span lang="EN-US">Deny()</span><span style="FONT-FAMILY: 宋体">方法：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">using System;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">using System.IO;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">using System.Security;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">using System.Security.Permissions;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">namespace Wrox.ProcSharp.Security</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> class SecurityApp4</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> static void Main(string[] args)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> CodeAccessPermission permission = </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> new FileIOPermission(FileIOPermissionAccess.AllAccess,@"C:\");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> permission.Deny();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> UntrustworthyClass.Method();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> CodeAccessPermission.RevertDeny();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> class UntrustworthyClass</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> public static void Method()</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> try</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> StreamReader din = File.OpenText(@"C:\textfile.txt"); </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> catch</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine("Failed to open file");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如果执行这段代码，结果将显示出“</span><span lang="EN-US">Failed to open file</span><span style="FONT-FAMILY: 宋体">”这样的信息，原因是不可信的类没有访问本地磁盘的权限。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">注意，</span><span lang="EN-US" style="LETTER-SPACING: -0.1pt">Deny()</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">是在权限对象的实例上调用的，而</span><span lang="EN-US" style="LETTER-SPACING: -0.1pt">RevertDeny()</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">是静态调用的。其</span><span style="FONT-FAMILY: 宋体">原因是</span><span lang="EN-US">RevertDeny()</span><span style="FONT-FAMILY: 宋体">回复当前堆栈帧中所有的拒绝请求，这意味着如果多次调用了</span><span lang="EN-US">Deny()</span><span style="FONT-FAMILY: 宋体">，则只需调用一次</span><span lang="EN-US">RevertDeny()</span><span style="FONT-FAMILY: 宋体">。</span></p></div>
<!-- page -->
<div class="page" style="text-align: center">
<a href="100165426.htm">上一页</a> <a href="index.html">首页</a> <a href="100165428.htm">下一页</a>
</div>
<div style="margin: 0px auto; width: 700px; border: solid 1px #0b5f98;">
<div style="float: left; width: 16px; background-color: #0b5f98; color: White; padding: 1px;">
图书导读
</div>
<div style="float: right; width: 670px; text-align: left; line-height: 16pt; padding-left: 2px">
<!--导读-->
<h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165427.htm'><font color='red'>14.2.4 拒绝权限</font></a></h1>
<div id="divRealteNod2" style="padding-left: 2px">
<div style='float:left;width:49%'>·<a href='100165424.htm'>14.2.1 要求权限</a></div><div style='float:right;width:49%'>·<a href='100165425.htm'>14.2.2 请求权限</a></div><div style='float:left;width:49%'>·<a href='100165426.htm'>14.2.3 隐式的权限</a></div><div style='float:right;width:49%'>·<a href='100165428.htm'>14.2.5 断言权限</a></div><div style='float:left;width:49%'>·<a href='100165429.htm'>14.2.6 创建代码访问权限</a></div><div style='float:right;width:49%'>·<a href='100165430.htm'>14.2.7 声明的安全性</a></div></div>
</div>
</div>
</div>
</div>
</body>
</html>
⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?