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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="17.10.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="17.10.2.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="16.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="18.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="17.htm">17</a></span><span class="clause-title-previous"> Classes</span></span><span class="clause-depth"><a href="17.9.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="17.11.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="17.10.htm">17.10</a></span><span class="clause-title-previous"> Instance constructors</span></span><span class="clause-depth"><a href="17.10.1.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="17.10.2.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">17.10.1</span><span class="clause-title"> Constructor initializers</span></span><span class="locator">
Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>All instance constructors (except those for class object) implicitly include an invocation of another instance constructor immediately before the <span class="non-terminal"><a href="17.10.htm#constructor-body">constructor-body</a></span>.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P1S2"></a>The constructor to implicitly invoke is determined by the constructor-initializer: </span><ul><li><span class="sentence"><span class="sentence-number">3</span> <a name="P1S3"></a> An instance constructor initializer of the form base(argument-listopt) causes an instance constructor from the direct base class to be invoked.</span> <span class="sentence"><span class="sentence-number">4</span> <a name="P1S4"></a>That constructor is selected using <span class="non-terminal"><a href="14.4.1.htm#argument-list">argument-list</a></span> and the overload resolution rules of <a href="14.4.2.htm">§14.4.2</a>.</span> <span class="sentence"><span class="sentence-number">5</span> <a name="P1S5"></a>The set of candidate instance constructors consists of all accessible instance constructors declared in the direct base class.</span> <span class="sentence"><span class="sentence-number">6</span> <a name="P1S6"></a>If this set is empty, or if a single best instance constructor cannot be identified, a compile-time error occurs.</span> </li><li><span class="sentence"><span class="sentence-number">7</span> <a name="P1S7"></a> An instance constructor initializer of the form this(argument-listopt) causes an instance constructor from the class itself to be invoked.</span> <span class="sentence"><span class="sentence-number">8</span> <a name="P1S8"></a>The constructor is selected using <span class="non-terminal"><a href="14.4.1.htm#argument-list">argument-list</a></span> and the overload resolution rules of <a href="14.4.2.htm">§14.4.2</a>.</span> <span class="sentence"><span class="sentence-number">9</span> <a name="P1S9"></a>The set of candidate instance constructors consists of all accessible instance constructors declared in the class itself.</span> <span class="sentence"><span class="sentence-number">10</span> <a name="P1S10"></a>If that set is empty, or if a single best instance constructor cannot be identified, a compile-time error occurs.</span> <span class="sentence"><span class="sentence-number">11</span> <a name="P1S11"></a>If an instance constructor declaration includes a constructor initializer that invokes the constructor itself, a compile-time error occurs.</span> </li></ul></span><span class="locator">
Paragraph 2</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P2S1"></a>If an instance constructor has no constructor initializer, a constructor initializer of the form base() is implicitly provided.</span> <span class="note">[Note: Thus, an instance constructor declaration of the form <pre class="code-example">
C(...) {...}
</pre>is exactly equivalent to <pre class="code-example">
C(...): base() {...}
</pre>end note]</span> </span><span class="locator">
Paragraph 3</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P3S1"></a>The scope of the parameters given by the <span class="non-terminal"><a href="17.5.1.htm#formal-parameter-list">formal-parameter-list</a></span> of an instance constructor declaration includes the constructor initializer of that declaration.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P3S2"></a>Thus, a constructor initializer is permitted to access the parameters of the constructor.</span> <span class="example">[Example: For example: <pre class="code-example">
class A
{
public A(int x, int y) {}
}
class B: A
{
public B(int x, int y): base(x + y, x - y) {}
}
</pre>end example]</span> </span><span class="locator">
Paragraph 4</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P4S1"></a>An instance constructor initializer cannot access the instance being created.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P4S2"></a>Therefore it is a compile-time error to reference this in an argument expression of the constructor initializer, as it is a compile-time error for an argument expression to reference any instance member through a <span class="non-terminal"><a href="14.5.2.htm#simple-name">simple-name</a></span>.</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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