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📁 This ECMA Standard specifies the form and establishes the interpretation of programs written in the
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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="17.10.2.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="17.10.4.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="17.10.2.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="17.10.4.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">17.10.3</span><span class="clause-title"> Constructor execution</span></span><span class="locator">
     Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>Variable initializers are transformed into assignment statements, and these assignment statements are executed before the invocation of the base class instance constructor.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P1S2"></a>This ordering ensures that all instance fields are initialized by their variable initializers before any statements that have access to that instance are executed.</span> <span class="example">[Example: For example: <pre class="code-example">
using System;  
class A  
{  
   public A() {  
      PrintFields();  
   }  
   public virtual void PrintFields() {}  
}  
class B: A  
{  
   int x = 1;  
   int y;  
   public B() {  
      y = -1;  
   }  
   public override void PrintFields() {  
      Console.WriteLine("x = {0}, y = {1}", x, y);  
   }  
}  
</pre></span></span><span class="paragraph"><span class="example">When new B() is used to create an instance of B, the following output is produced: <pre class="code-example">
x = 1, y = 0  
</pre></span></span><span class="paragraph"><span class="example">The value of x is 1 because the variable initializer is executed before the base class instance constructor is invoked. However, the value of y is 0 (the default value of an <span class="keyword">int</span>) because the assignment to y is not executed until after the base class constructor returns. </span></span><span class="paragraph"><span class="example">It is useful to think of instance variable initializers and constructor initializers as statements that are automatically inserted before the <span class="non-terminal"><a href="17.10.htm#constructor-body">constructor-body</a></span>. The example <pre class="code-example">
using System;  
using System.Collections;  
class A  
{  
   int x = 1, y = -1, count;  
   public A() {  
      count = 0;  
   }  
   public A(int n) {  
      count = n;  
   }  
}  
class B: A  
{  
   double sqrt2 = Math.Sqrt(2.0);  
   ArrayList items = new ArrayList(100);  
   int max;  
   public B(): this(100) {  
      items.Add("default");  
   }  
   public B(int n): base(n - 1) {  
      max = n;  
   }  
}  
</pre>contains several variable initializers; it also contains constructor initializers of both forms (base and this). The example corresponds to the code shown below, where each comment indicates an automatically inserted statement (the syntax used for the automatically inserted constructor invocations isn't valid, but merely serves to illustrate the mechanism). <pre class="code-example">
using System.Collections;  
class A  
{  
   int x, y, count;  
   public A() {  
      x = 1;         // Variable initializer  
      y = -1;         // Variable initializer  
      object();        // Invoke object() constructor  
      count = 0;  
   }  
   public A(int n) {  
      x = 1;         // Variable initializer  
      y = -1;         // Variable initializer  
      object();        // Invoke object() constructor  
      count = n;  
   }  
}  
class B: A  
{  
   double sqrt2;  
   ArrayList items;  
   int max;  
   public B(): this(100) {  
      B(100);         // Invoke B(int) constructor  
      items.Add("default");  
   }  
   public B(int n): base(n - 1) {  
      sqrt2 = Math.Sqrt(2.0);   // Variable initializer  
      items = new ArrayList(100);  // Variable initializer  
      A(n - 1);        // Invoke A(int) constructor  
      max = n;  
   }  
}  
</pre>end example]</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>
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