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POC# Proper solution needed for "can't specify constructor/static method in interface" problem
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copied!<p>Okay, I need some help here.</p> <p>This is the same old <strong>"can't use an interface to enforce constructors/static methods"</strong> problem.</p> <p><strong>WHAT IS THE PROPER OO DESIGN THEN??</strong></p> <p>I have a set of data entities (Entity Framework stuff) for which I wrote partial class methods to convert to/from XML (XElement objects).</p> <p>I have an instance method to "save" XML:</p> <pre><code>// Convert entity to XML public XElement ToXml() {} </code></pre> <p>...and I have a constructor to "read" XML:</p> <pre><code>// Create entity from XML constructor. public MyEntity(XElement) {} </code></pre> <p>Alternatively, I could use a static factory method to "read" XML:</p> <pre><code>public static MyEntity ParseXml(XElement) {} </code></pre> <p><strong>The dilemma:</strong></p> <ol> <li><p>I could create an interface that mandates the "save" <code>ToXml()</code> method, but what good is that if it only addresses half the problem? An interface can't enforce either of the "load" methods.</p></li> <li><p>I could rely on my own good intent to create these methods without any sort of contract.</p></li> <li><p>I could create a static class filled with redundant methods like <code>XmlToEntity1()</code> and <code>XmlToEntity2()</code>, etc... (Now I've described a good 'generics' problem.) However, the specific conversion code (which is specific to each entity) would create separate methods or switch/case for each and seems to belong inside the entity classes, not in some other class, no?</p></li> </ol> <p><strong>If an experienced C# coder can show a good design for this common problem I think I would learn a lot from it.</strong></p> <p>Happy 4th of July!</p> <h1>Possible Solution 1</h1> <p>A single <code>XmlSerializer</code> class with two static generic methods:</p> <pre><code>public static T Deserialize<T>(XElement xml) {} public static XElement Serialize<T>(T entity) {} </code></pre> <ul> <li>Pro: Only one class (no interface needed)</li> <li>Pro: Separates serialization responsibility from entity classes.</li> <li>Con: Would still require separate methods or switch/case blocks for each entity type supported.</li> <li>Con: ? Not extensible -- have to modify this class each time an entity changed or added/deleted.</li> </ul> <h1>Possible lessons learned?</h1> <p>The "can't use interface for constructors and static methods" problem might be a symptom of:</p> <ol> <li>Violating the SRP (Single Responsibility Principal).</li> <li>Violating the SoC (Separation of Concern) principal.</li> </ol>

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