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    <p>Well, in this case, if you can't use Memoization, you're rather restricted since you can really only use the stack as your cache: You've got no way to declare a new variable at the scope you'll need. All I can think of (and I'm not claiming it will be pretty) that will do what you want but retain the composability you need would be something like...</p> <pre><code>private static bool TestWith&lt;T&gt;(T cached, Func&lt;T, bool&gt; predicate) { return predicate(cached); } public static Expression&lt;Func&lt;Potion, bool&gt;&gt; ContainsIngredients(string ingredientType, params string[] ingredients) { var predicate = PredicateBuilder.False&lt;Potion&gt;(); // Here, I'm accessing p.Ingredients several times in one // expression. Is there any way to cache this value and // reference the cached value in the expression? foreach (var ingredient in ingredients) { var temp = ingredient; predicate = predicate.Or ( p =&gt; TestWith(p.Ingredients, i =&gt; i != null &amp;&amp; i.Contains(ingredientType) &amp;&amp; i.Get(ingredientType).Contains(temp)); } return predicate; } </code></pre> <p>You could combine together the results from multiple TestWith calls into a more complex boolean expression where required - caching the appropriate expensive value with each call - or you can nest them within the lambdas passed as the second parameter to deal with your complex deep hierarchies.</p> <p>It would be quite hard to read code though and since you might be introducing a bunch more stack transitions with all the TestWith calls, whether it improves performance would depend on just how expensive your ExpensiveCall() was.</p> <p>As a note, there won't be any inlining in the original example as suggested by another answer since the expression compiler doesn't do that level of optimisation as far as I know.</p>
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    1. POIs it possible to cache a value evaluated in a lambda expression?
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