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POC# .Net 3.5 Using Overloaded Indexers with different return types
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  1. POC# .Net 3.5 Using Overloaded Indexers with different return types
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    copied!<p>I have a parent class which is essentially a glorified list. It's extended by several subclasses for various functionalities.</p> <pre><code>public class HierarchialItemList&lt;ItemType&gt; : IEnumerable&lt;ItemType&gt; { public ItemType this[String itemCode] { get { foreach (IHierarchialItem curItem in hierarchialItems) { if (curItem.Code.Equals(itemCode, StringComparison.CurrentCultureIgnoreCase)) { return ((ItemType)curItem); } } return (default(ItemType)); } } public ItemType this[Int32 index] { get { return (hierarchialItems[index]); } } } public class DatabaseList : HierarchialItemList&lt;Database&gt; { public DatabaseList this[CommonDatabaseType typeToFilter] { get { DatabaseList returnList = new DatabaseList(); foreach(Database curDatabase in this) { if (curDatabase.DatabaseType.Equals(typeToFilter)) { returnList.Add(curDatabase); } } return (returnList); } } public DatabaseList this[Environments.RMSEnvironment environmentToFilter] { get { DatabaseList returnList = new DatabaseList(); foreach(Database curDatabase in this) { if (curDatabase.ParentEnvironment.Equals(environmentToFilter)) { returnList.Add(curDatabase); } } return (returnList); } } } </code></pre> <p>The problem is that C# thinks that this:</p> <p><code>Database testDatabase = sampleDatabaseList[0];</code></p> <p>Is an error and that the indexer should be returning a DatabaseList, not a Database. You and I both know that's false. Any workarounds or do all indexers have to have the same return type?</p> <p>Edit: I just figured out that it's because of using an enumeration as an indexer which is internally an integer. Still, any way to use both an enumeration and an integer?</p> <p>Edit 2: As requested, here is some compiliable test code which demonstrates the problem.</p> <pre><code>using System; using System.Collections.Generic; namespace CSQT { class A&lt;T&gt; { List&lt;T&gt; temp; public A() { temp = new List&lt;T&gt;(); } public void AddItem(T itemToAdd) { temp.Add(itemToAdd); } public T this[String code] { get { return (temp[0]); } } public T this[Int32 index] { get { return (temp[index]); } } } class B : A&lt;String&gt; { public B() : base() { } public B this[BTypes testType] { get { return (this); } } } enum BTypes { TEMP1, TEMP2 }; class C { public C() { B temp = new B(); //Compile error: Cannot implicitly convert type 'CSQT.B' to 'string' String temp2 = temp[0]; //Compile error: Cannot convert type 'CSQT.B' to 'string' String temp3 = (String)temp[0]; //This compiles and runs but instead of going to A.this[int32], it goes to B.this[BTypes testType] B temp4 = temp[0]; } } } </code></pre>
 

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