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    <p>This is not a matter of performance, as the two have completely different semantics.</p> <p>The first gives you a way to use one object to find another object.</p> <p>The second gives you a way to use one object to find another object, in which you can use yet another object to find a third object.</p> <p>There is slightly different functionality in terms of how these can be later extended.</p> <p>Most generally, I'd use <code>Dictionary&lt;Tuple&lt;string, string&gt;, string&gt;</code>. This would give me a composite key that is clearly a composite key.</p> <p>Actually, that's not true, I'd create a new class. How is that not an option? Still, if it was homework and "do not create a new class" was part of the question, I'd use <code>Dictionary&lt;Tuple&lt;string, string&gt;, string&gt;</code>.</p> <p>Edit:</p> <pre><code>class DialectQuery : IEquatable&lt;DialectQuery&gt; { public Dialect{get;private set} public Name{get;private set;} public DialectQuery(string dialect, string name) { Dialect = dialect; Name = name; } public bool Equals(DialectQuery other) { return other != null &amp;&amp; Name == other.Name &amp;&amp; Dialect == other.Dialect; } public override bool Equals(object other) { return Equals((object)other); } public override int GetHashCode() { int dHash = Dialect.GetHashCode(); return (dHash &lt;&lt; 16 | dHash &gt;&gt; 16) ^ Name.GetHashCode(); } } </code></pre> <p>So far it behaves exactly the same as Tuple. Now though if I get a change request that dialects must be case-insensitive but query names case-sensitive, or that dialects are codes and therefore require invariant comparison but names are human-input and therefore require culture-aware comparison, or anything else, I've got two simple changes to make.</p> <p>YAGNI doesn't apply, it's not coding a massive object "in case you need it", it's defining a good "okay, I probably don't need it, but if I do it'll go here" point.</p>
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    1. PO Dictionary object performance
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    1. USJon Hanna
    1. USJon Hanna
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    1. COIf you were to use a class how would you structure it in order to be able to produce the same or better performance while still offering the same functionality? I need to be able to construct it and populate it with all three variables (more than one of each straight from a table in a database) and then be able to pick query strings out quickly using both key variables. To me it seems far simpler to use the first option I mention.
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    2. COAs a simple class with two properties and an equality override. It's half a minute's coding but nicely deals with "oh, dialects should be case-insensitive but queries shouldn't" or any other extensions that arise in the spec down the line.
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    3. COHow exactly would that work for my scenario? If I need to effectively produce a list of sql commands that can be accessed by two keys? The reason I want to use a dictionary object is that once populated with all the necessary dialects, query names and queries upon instantiating my sql factory class I can access whichever query I need by checking the composite key for a dialect and query name. May just be me having a slow brain day but I can't see how a class could be used to do this? All of the three variables are linked like this dialect>query name>query. How could you do that with properties
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