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    <p>The only way you'll be able to do this if you have a custom collection with generic overloads for Add and Get methods. But that would mean you can ask for the wrong type when reading the key out, so it doesn't gain you much (if anything) over doing the cast yourself when you call your Get method.</p> <p>However, if you can push the generic type into the key then that could work. Something like (untested code here)</p> <pre><code>sealed class MyDictionaryKey&lt;T&gt; { } class MyDictionary { private Dictionary&lt;object, object&gt; dictionary = new Dictionary&lt;object, object&gt;(); public void Add&lt;T&gt;(MyDictionaryKey&lt;T&gt; key, T value) { dictionary.Add(key, value); } public bool TryGetValue&lt;T&gt;(MyDictionaryKey&lt;T&gt; key, out T value) { object objValue; if (dictionary.TryGetValue(key, out objValue)) { value = (T)objValue; return true; } value = default(T); return false; } public T Get&lt;T&gt;(MyDictionaryKey&lt;T&gt; key) { T value; if (!TryGetValue(key, out value)) throw new KeyNotFoundException(); return value; } } </code></pre> <p>Then you can define your keys like:</p> <pre><code>static readonly MyDictionaryKey&lt;string&gt; NameKey = new MyDictionaryKey&lt;string&gt;(); static readonly MyDictionaryKey&lt;double&gt; HeightKey = new MyDictionaryKey&lt;double&gt;(); </code></pre> <p>and use it like</p> <pre><code>var myDict = new MyDictionary(); myDict.Add(NameKey, "Bill"); // this will take a string myDict.Add(HeightKey , 1.2); // this will take a double string name = myDict.Get(NameKey); // will return a string double height = myDict.Get(HeightKey); // will return a double </code></pre>
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    1. COThank you. As others have said, this is less of a practical than academic inquiry, but you hit the head on the nail in inferring that I wanted the key to determine the expected type of the item retrieved.
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