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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="13.4.3.htm"><img src="previous.gif" alt="previous" border="0" /></a><a href="14.htm"><img src="next.gif" alt="next" border="0" /></a></span><span class="clause-depth"><a href="12.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="14.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="13.htm">13</a></span><span class="clause-title-previous"> Conversions</span></span><span class="clause-depth"><a href="13.3.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="13.4.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number-link"><a href="13.4.htm">13.4</a></span><span class="clause-title-previous"> User-defined conversions</span></span><span class="clause-depth"><a href="13.4.3.htm"><img src="previous.gif" alt="previous at this level" border="0" /></a><a href="13.4.4.htm"><img src="next.gif" alt="next at this level" border="0" /></a> <span class="clause-number">13.4.4</span><span class="clause-title"> User-defined explicit conversions</span></span><span class="locator">
     Paragraph 1</span><span class="paragraph"><span class="sentence"><span class="sentence-number">1</span> <a name="P1S1"></a>A user-defined explicit conversion from type S to type T is processed as follows: </span><ul><li><span class="sentence"><span class="sentence-number">2</span> <a name="P1S2"></a> Find the set of types, D, from which user-defined conversion operators will be considered.</span> <span class="sentence"><span class="sentence-number">3</span> <a name="P1S3"></a>This set consists of S (if S is a class or struct), the base classes of S (if S is a class), T (if T is a class or struct), and the base classes of T (if T is a class).</span> </li><li><span class="sentence"><span class="sentence-number">4</span> <a name="P1S4"></a> Find the set of applicable user-defined conversion operators, U.</span> <span class="sentence"><span class="sentence-number">5</span> <a name="P1S5"></a>This set consists of the user-defined implicit or explicit conversion operators declared by the classes or structs in D that convert from a type encompassing or encompassed by S to a type encompassing or encompassed by T.</span> <span class="sentence"><span class="sentence-number">6</span> <a name="P1S6"></a>If U is empty, the conversion is undefined and a compile-time error occurs.</span> </li><li><span class="sentence"><span class="sentence-number">7</span> <a name="P1S7"></a> Find the most specific source type, SX, of the operators in U: </span></li><ul><li><span class="sentence"><span class="sentence-number">8</span> <a name="P1S8"></a> If any of the operators in U convert from S, then SX is S.</span> </li><li><span class="sentence"><span class="sentence-number">9</span> <a name="P1S9"></a> Otherwise, if any of the operators in U convert from types that encompass S, then SX is the most encompassed type in the combined set of source types of those operators.</span> <span class="sentence"><span class="sentence-number">10</span> <a name="P1S10"></a>If no most encompassed type can be found, then the conversion is ambiguous and a compile-time error occurs.</span> </li><li><span class="sentence"><span class="sentence-number">11</span> <a name="P1S11"></a> Otherwise, SX is the most encompassing type in the combined set of source types of the operators in U.</span> <span class="sentence"><span class="sentence-number">12</span> <a name="P1S12"></a>If no most encompassing type can be found, then the conversion is ambiguous and a  compile-time error occurs.</span> </li></ul><li><span class="sentence"><span class="sentence-number">13</span> <a name="P1S13"></a> Find the most specific target type, TX, of the operators in U: </span></li><ul><li><span class="sentence"><span class="sentence-number">14</span> <a name="P1S14"></a> If any of the operators in U convert to T, then TX is T.</span> </li><li><span class="sentence"><span class="sentence-number">15</span> <a name="P1S15"></a> Otherwise, if any of the operators in U convert to types that are encompassed by T, then TX is the most encompassing type in the combined set of target types of those operators.</span> <span class="sentence"><span class="sentence-number">16</span> <a name="P1S16"></a>If no most encompassing type can be found, then the conversion is ambiguous and a compile-time error occurs.</span> </li><li><span class="sentence"><span class="sentence-number">17</span> <a name="P1S17"></a> Otherwise, TX is the most encompassed type in the combined set of target types of the operators in U.</span> <span class="sentence"><span class="sentence-number">18</span> <a name="P1S18"></a>If no most encompassed type can be found, then the conversion is ambiguous and a compile-time error occurs.</span> </li></ul><li><span class="sentence"><span class="sentence-number">19</span> <a name="P1S19"></a> If U contains exactly one user-defined conversion operator that converts from SX to TX, then this is the most specific conversion operator.</span> <span class="sentence"><span class="sentence-number">20</span> <a name="P1S20"></a>If no such operator exists, or if more than one such operator exists, then the conversion is ambiguous and a compile-time error occurs.</span> <span class="sentence"><span class="sentence-number">21</span> <a name="P1S21"></a>Otherwise, the user-defined conversion is applied: </span></li><ul><li><span class="sentence"><span class="sentence-number">22</span> <a name="P1S22"></a> If S is not SX, then a standard explicit conversion from S to SX is performed.</span> </li><li><span class="sentence"><span class="sentence-number">23</span> <a name="P1S23"></a> The most specific user-defined conversion operator is invoked to convert from SX to TX.</span> </li><li><span class="sentence"><span class="sentence-number">24</span> <a name="P1S24"></a> If TX is not T, then a standard explicit conversion from TX to T is performed.</span> <span class="table-line"></span>
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