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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="10.5.1.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="10.5.3.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="9.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="11.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="10.htm">10</a></span><span class="clause-title-previous"> Basic concepts</span></span><span class="clause-depth"><a href="10.4.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="10.6.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="10.5.htm">10.5</a></span><span class="clause-title-previous"> Member access</span></span><span class="clause-depth"><a href="10.5.1.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="10.5.3.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">10.5.2</span><span class="clause-title"> Accessibility domains</span></span><span class="locator">
Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>The accessibility domain of a member consists of the (possibly disjoint) sections of program text in which access to the member is permitted.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P1S2"></a>For purposes of defining the accessibility domain of a member, a member is said to be top-level if it is not declared within a type, and a member is said to be nested if it is declared within another type.</span> <span class="sentence"><span class="sentence-number">3</span> <a name="P1S3"></a>Furthermore, the text of an assembly is defined as all source text contained in all source files of that assembly, and the source text of a type is defined as all source text contained between the opening and closing "{" and "}" tokens in the <span class="non-terminal"><a href="17.1.3.htm#class-body">class-body</a></span>, <span class="non-terminal"><a href="18.1.3.htm#struct-body">struct-body</a></span>, <span class="non-terminal"><a href="20.1.3.htm#interface-body">interface-body</a></span>, or <span class="non-terminal"><a href="21.1.htm#enum-body">enum-body</a></span> of the type (including, possibly, types that are nested within the type).</span> </span><span class="locator">
Paragraph 2</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P2S1"></a>The accessibility domain of a predefined type (such as object, <span class="keyword">int</span>, or <span class="keyword">double</span>) is unlimited.</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 accessibility domain of a top-level type T that is declared in a program P is defined as follows: </span><ul><li><span class="sentence"><span class="sentence-number">2</span> <a name="P3S2"></a> If the declared accessibility of T is public, the accessibility domain of T is the program text of P and any program that references P.</span> </li><li><span class="sentence"><span class="sentence-number">3</span> <a name="P3S3"></a> If the declared accessibility of T is internal, the accessibility domain of T is the program text of P.</span> </li></ul></span><span class="paragraph"><span class="note">[Note: From these definitions it follows that the accessibility domain of a top-level type is always at least the program text of the program in which that type is declared. end note]</span> </span><span class="locator">
Paragraph 4</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P4S1"></a>The accessibility domain of a nested member M declared in a type T within a program P, is defined as follows (noting that M itself may possibly be a type): </span><ul><li><span class="sentence"><span class="sentence-number">2</span> <a name="P4S2"></a> If the declared accessibility of M is public, the accessibility domain of M is the accessibility domain of T.</span> </li><li><span class="sentence"><span class="sentence-number">3</span> <a name="P4S3"></a> If the declared accessibility of M is protected internal, let D be the union of the program text of P and the program text of any type derived from T, which is declared outside P.</span> <span class="sentence"><span class="sentence-number">4</span> <a name="P4S4"></a>The accessibility domain of M is the intersection of the accessibility domain of T with D.</span> </li><li><span class="sentence"><span class="sentence-number">5</span> <a name="P4S5"></a> If the declared accessibility of M is protected, let D be the union of the program text of T and the program text of any type derived from T.</span> <span class="sentence"><span class="sentence-number">6</span> <a name="P4S6"></a>The accessibility domain of M is the intersection of the accessibility domain of T with D.</span> </li><li><span class="sentence"><span class="sentence-number">7</span> <a name="P4S7"></a> If the declared accessibility of M is internal, the accessibility domain of M is the intersection of the accessibility domain of T with the program text of P.</span> </li><li><span class="sentence"><span class="sentence-number">8</span> <a name="P4S8"></a> If the declared accessibility of M is private, the accessibility domain of M is the program text of T.</span> </li></ul></span><span class="paragraph"><span class="note">[Note: From these definitions it follows that the accessibility domain of a nested member is always at least the program text of the type in which the member is declared. Furthermore, it follows that the accessibility domain of a member is never more inclusive than the accessibility domain of the type in which the member is declared. end note]</span> </span><span class="paragraph"><span class="note">[Note: In intuitive terms, when a type or member M is accessed, the following steps are evaluated to ensure that the access is permitted: <ul><li> First, if M is declared within a type (as opposed to a compilation unit or a namespace), a compile-time error occurs if that type is not accessible. </li><li> Then, if M is public, the access is permitted. </li><li> Otherwise, if M is protected internal, the access is permitted if it occurs within the program in which M is declared, or if it occurs within a class derived from the class in which M is declared and takes place through the derived class type (<a href="10.5.3.htm">§10.5.3</a>). </li><li> Otherwise, if M is protected, the access is permitted if it occurs within the class in which M is declared, or if it occurs within a class derived from the class in which M is declared and takes place through the derived class type (<a href="10.5.3.htm">§10.5.3</a>). </li><li> Otherwise, if M is internal, the access is permitted if it occurs within the program in which M is declared. </li><li> Otherwise, if M is private, the access is permitted if it occurs within the type in which M is declared. </li><li> Otherwise, the type or member is inaccessible, and a compile-time error occurs. end note]</li></ul></span> </span><span class="paragraph"><span class="example">[Example: In the example <pre class="code-example">
public class A
{
public static int X;
internal static int Y;
private static int Z;
}
internal class B
{
public static int X;
internal static int Y;
private static int Z;
public class C
{
public static int X;
internal static int Y;
private static int Z;
}
private class D
{
public static int X;
internal static int Y;
private static int Z;
}
}
</pre>the classes and members have the following accessibility domains: <ul><li> The accessibility domain of A and A.X is unlimited. </li><li> The accessibility domain of A.Y, B, B.X, B.Y, B.C, B.C.X, and B.C.Y is the program text of the containing program. </li><li> The accessibility domain of A.Z is the program text of A. </li><li> The accessibility domain of B.Z and B.D is the program text of B, including the program text of B.C and B.D. </li><li> The accessibility domain of B.C.Z is the program text of B.C. </li><li> The accessibility domain of B.D.X, B.D.Y, and B.D.Z is the program text of B.D. </li></ul></span></span><span class="paragraph"><span class="example">As the example illustrates, the accessibility domain of a member is never larger than that of a containing type. For example, even though all X members have public declared accessibility, all but A.X have accessibility domains that are constrained by a containing type. end example]</span> </span><span class="locator">
Paragraph 5</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P5S1"></a>As described in <a href="10.4.htm">§10.4</a>, all members of a base class, except for instance constructors, destructors, and static constructors are inherited by derived types.</span> <span class="sentence"><span class="sentence-number">2</span> <a name="P5S2"></a>This includes even private members of a base class.</span> <span class="sentence"><span class="sentence-number">3</span> <a name="P5S3"></a>However, the accessibility domain of a private member includes only the program text of the type in which the member is declared.</span> <span class="example">[Example: In the example <pre class="code-example">
class A
{
int x;
static void F(B b) {
b.x = 1; // Ok
}
}
class B: A
{
static void F(B b) {
b.x = 1; // Error, x not accessible
}
}
</pre>the B class inherits the private member x from the A class. Because the member is private, it is only accessible within the <span class="non-terminal"><a href="17.1.3.htm#class-body">class-body</a></span> of A. Thus, the access to b.x succeeds in the A.F method, but fails in the B.F method. 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>⌨️ 快捷键说明
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