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PODefining Generic Objects with class and interface
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  1. PODefining Generic Objects with class and interface
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    copied!<p>I'm having some trouble figuring out how to require a class has extended an interface when working with generic objects. I find this to be difficult to explain, but I want to be able to require a class &amp; an interface when creating my generic object.</p> <p>I've created the simplest version of this that I can think of - hopefully that will explain my problem better than I can.</p> <pre><code>abstract class Base {} class Class1 : Base, IComparable&lt;Base&gt; { public int CompareTo(Base other) { return GetHashCode().CompareTo(other.GetHashCode()); } } class Class2 : Base, IComparable&lt;Base&gt; { public int CompareTo(Base other) { return GetHashCode().CompareTo(other.GetHashCode()); } } class Class3 : Base {} class Program { // This list should only accept objects that extend (Base &amp; IComparable&lt;Base&gt;) public static List&lt;Base&gt; BigList = new List&lt;Base&gt;(); static void Main(string[] args) { Class1 c1 = new Class1(); Class2 c2 = new Class2(); Class3 c3 = new Class3(); BigList.Add(c1); BigList.Add(c2); // This should not be allowed because Class3 does not extend IComparable&lt;Base&gt; BigList.Add(c3); Check(new Class1()); } public static void Check(Base bb) { foreach (Base b in BigList) { // Assert that this is true IComparable&lt;Base&gt; c = (IComparable&lt;Base&gt;)b; if (c.CompareTo(bb) &lt; 0) Console.WriteLine("Less Than"); else if (c.CompareTo(bb) == 0) Console.WriteLine("Equal"); else if (c.CompareTo(bb) &gt; 0) Console.WriteLine("Greater Than"); } } } </code></pre> <p>As you can see from the inline comments in the code, I'd like the list <code>BigList</code> to require that the objects being added extend <code>Base</code> <strong>AND</strong> implements <code>IComparable&lt;Base&gt;</code>. This isn't really multiple inheritance though because it's only one class (and an interface).</p> <p>Does anyone know of a way to do this?</p> <p><strong>EDIT</strong></p> <p>Thanks for the comments everyone. Basically the answers come in two flavors: Create an Intermediate class, or use <code>List&lt;IComparable&lt;Base&gt;&gt;</code>. #2 isn't an option because there is logic in Base that we do actually need. #1 is the most viable option, and the one that we are <em>grudgingly</em> going with. The concern with this approach is the amount of mess and complexity this will add in the actual class hierarchy.</p> <p>Regardless if C# won't let us do what we want to do then we will have to do it with the intermediate classes. Thanks everyone.</p>
 

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