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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>Hyperlinked ECMA C# Language Specification</title><meta name="author" content="Jon Jagger" /><link rel="stylesheet" href="ecma334.css"></link></head><body><div align="right"><em><a href="http://www.jaggersoft.com">Jon Jagger</a></em></div><div align="right"><a href="mailto:jon@jaggersoft.com">jon@jaggersoft.com</a></div><form method="get" action="http://search.atomz.com/search/"><input size="30" name="sp-q"></input><input type="submit" value="Search C# Spec"></input><input type="hidden" name="sp-a" value="sp10024177"></input><input type="hidden" name="sp-f" value="ISO-8859-1"></input></form><a href="toc.htm">Table of Contents</a> <a href="1.htm">1</a> <a href="2.htm">2</a> <a href="3.htm">3</a> <a href="4.htm">4</a> <a href="5.htm">5</a> <a href="6.htm">6</a> <a href="7.htm">7</a> <a href="8.htm">8</a> <a href="9.htm">9</a> <a href="10.htm">10</a> <a href="11.htm">11</a> <a href="12.htm">12</a> <a href="13.htm">13</a> <a href="14.htm">14</a> <a href="15.htm">15</a> <a href="16.htm">16</a> <a href="17.htm">17</a> <a href="18.htm">18</a> <a href="19.htm">19</a> <a href="20.htm">20</a> <a href="21.htm">21</a> <a href="22.htm">22</a> <a href="23.htm">23</a> <a href="24.htm">24</a> <a href="25.htm">25</a> <a href="notes.htm">Notes</a> <a href="HyperlinkedCSharpECMA.zip">Download</a><span class="ruler"></span><span class="heading">ECMA-334 C# Language Specification</span><span class="navigate"><a href="8.7.10.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="8.8.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="7.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="9.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="8.htm">8</a></span><span class="clause-title-previous"> Language Overview</span></span><span class="clause-depth"><a href="8.6.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="8.8.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="8.7.htm">8.7</a></span><span class="clause-title-previous"> Classes</span></span><span class="clause-depth"><a href="8.7.10.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="8.7.11.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">8.7.11</span><span class="clause-title"> Inheritance</span></span><span class="informative"><span class="paragraph">Classes support single inheritance, and the type object is the ultimate base class for all classes. </span><span class="paragraph">The classes shown in earlier examples all implicitly derive from object. The example <pre class="code-example">
using System;
class A
{
public void F() { Console.WriteLine("A.F"); }
}
</pre>shows a class A that implicitly derives from object. The example <pre class="code-example">
class B: A
{
public void G() { Console.WriteLine("B.G"); }
}
class Test
{
static void Main() {
B b = new B();
b.F(); // Inherited from A
b.G(); // Introduced in B
A a = b; // Treat a B as an A
a.F();
}
}
</pre>shows a class B that derives from A. The class B inherits A's F method, and introduces a G method of its own. </span><span class="paragraph">Methods, properties, and indexers can be virtual, which means that their implementation can be overridden in derived classes. The example <pre class="code-example">
using System;
class A
{
public virtual void F() { Console.WriteLine("A.F"); }
}
class B: A
{
public override void F() {
base.F();
Console.WriteLine("B.F");
}
}
class Test
{
static void Main() {
B b = new B();
b.F();
A a = b;
a.F();
}
}
</pre>shows a class A with a virtual method F, and a class B that overrides F. The overriding method in B contains a call, base.F(), which calls the overridden method in A. </span><span class="paragraph">A class can indicate that it is incomplete, and is intended only as a base class for other classes, by including the modifier abstract. Such a class is called an abstract class. An abstract class can specify abstract members-members that a non-abstract derived class must implement. The example <pre class="code-example">
using System;
abstract class A
{
public abstract void F();
}
class B: A
{
public override void F() { Console.WriteLine("B.F"); }
}
class Test
{
static void Main() {
B b = new B();
b.F();
A a = b;
a.F();
}
}
</pre>introduces an abstract method F in the abstract class A. The non-abstract class B provides an implementation for this method. </span></span><span class="ruler"></span><table><tr><td><table align="left" bgcolor="navy"><tr bgcolor="navy"><td><font face="Arial,sans-serif" size="6" color="yellow"><strong>{ JSL }</strong></font></td></tr></table></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Jagger Software Ltd</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>Company # 4070126</strong></font></td></tr><tr><td><font face="Arial,sans-serif" size="2" color="navy"><strong>VAT # 762 5213 42</strong></font></td></tr></table><img src="valid-html401.png" align="left" height="31" width="88" alt="Valid HTML 4.01" /><img src="vcss.gif" align="left" height="31" width="88" alt="Valid CSS" /></body></html>⌨️ 快捷键说明
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