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  1. PO
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    <p>There are a couple of things wrong here:</p> <p><code>Predicate&lt;double&gt;</code> is not an appropriate type to use as a <code>TKey</code>. The key for a dictionary is supposed to <em>identify</em> a value, not calculate a value.</p> <p>This wouldn't make any sense using lambdas either. Because they are anonymous, you wouldn't get any equivalence, and won't be able use a dictionary. </p> <p>See this code sample for an illustration:</p> <pre><code>Predicate&lt;double&gt; fn_1 = d =&gt; d == 34.0d; Predicate&lt;double&gt; fn_2 = d =&gt; d == 34.0d; // Note: There are not equal if (fn_1 == fn_2) Console.WriteLine("These are Equal?"); </code></pre> <p>If anything, you could use a list of delegates and execute each one to find the ones that match, but at that point you must expect multiple results. If you only want to get a single result, then you have to consider which <em>order</em> the predicates are stored within your list.</p> <p>Don't misuse <code>KeyValuePair</code> as a hack for not having <code>Tuple&lt;T1,T2&gt;</code>. It would be fairly easy to create a class that has both a Predicate and a SomeStruct. Look:</p> <pre><code>public class MySegment { public Predicate&lt;double&gt; Predicate {get;set;} public SomeStruct Result {get;set;} } </code></pre> <p>To go through a sequence of predicates, and find the matching ones would look like this:</p> <pre><code>... List&lt;MySegment&gt; list = new List&lt;MySegment&gt;(); ... list.Add(new MySegment { Predicate = d =&gt; d &lt; 10, Result = SomeStruct.Foo }); list.Add(new MySegment { Predicate = d =&gt; d &gt; 90, Result = SomeStruct.Bar }); ... public IEnumerable&lt;SomeStruct&gt; GetResults(double input) { foreach (var item in list) if (item.Predicate(input)) yield return item.Result; } </code></pre>
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    1. POHow to call Dictionary<K, V>.TryGetValue() where K : Predicate<T>, V : enum
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    1. USMatt Brunell
    1. USMatt Brunell
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    1. POHow to call Dictionary<K, V>.TryGetValue() where K : Predicate<T>, V : enum
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      1. VTUpMod
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    1. CO+1, for a clear description of the issues, though from a style standpoint I'd make GetResults `return from i in list where i.Predicate(input) select i.Result;`. Just a matter of preference, though.
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      1. USStriplingWarrior
    2. COThanks a lot! Only one note - predicates I have a unique (because describes segments [0;30], [70,100]) that's why I decided to use Dictionary or KVP.
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    3. CO@StriplingWarrior: `list.Where(item => item.Predicate(input))` also works to me properly
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