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copied!<p>You just need to express the specific types. For example:</p> <pre><code>Func<Func<int, int>, Func<int, int>> </code></pre> <p>represents a function which takes a (function converting an int to a second int) and returns a (function converting an int to a second int). Or to take two functions and return a third:</p> <pre><code>Func<Func<int, int>, Func<int, int>, Func<int, int>> </code></pre> <p>For example:</p> <pre><code>Func<Func<int, int>, Func<int, int>> applyTwice = (f => x => f(f(x)); </code></pre> <p>This can be returned generically by a method:</p> <pre><code>public static Func<Func<T,T>, Func<T,T>> ApplyTwice<T>() { return func => x => func(func(x)); } </code></pre> <p>If you want to sum two functions, you might do:</p> <pre><code>public static Func<int, int> Sum(Func<int, int> first, Func<int, int> second) { return x => first(x) + second(x); } </code></pre> <p>Now to apply it:</p> <pre><code>Func<int, int> doubler = x => x * 2; Func<int, int> squarer = x => x * x; Func<int, int> doublePlusSquare = Sum(doubler, squarer); Console.WriteLine(doublePlusSquare(5)); // Prints 35 </code></pre> <p>(Untested, but should be okay...)</p> <hr> <p>If you don't have C# 3 and .NET 3.5 available to you, then declare the following delegates:</p> <pre><code>public delegate TResult Func<TResult>(); public delegate TResult Func<T, TResult>(T arg); public delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2); </code></pre> <p>(There's more on my <a href="http://csharpindepth.com/Articles/Chapter1/Versions.aspx" rel="noreferrer">C# Versions page</a>.)</p> <p>Then you'll need to use anonymous methods, e.g.</p> <pre><code>public static Func<int, int> Sum(Func<int, int> first, Func<int, int> second) { return delegate(int x) { return first(x) + second(x); }; } Func<int, int> doubler = delegate (int x) { return x * 2; }; Func<int, int> squarer = delegate (int x) { return x * x; }; Func<int, int> doublePlusSquare = Sum(doubler, squarer); Console.WriteLine(doublePlusSquare(5)); // Prints 35 </code></pre>

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