Generic function declaration in C#

Question

I'm trying to create some stats about method call duration in a library. Instead of wrapping each method call to the library with lines to time and track it, I want to create a generic action and function which does these recurring steps.

E.g. for methods that don't return a value, I have created this:

    private readonly Action<string, Action> timedAction = (name, action) =>
    {
        var sw = Stopwatch.StartNew();
        action.Invoke();
        trackDuration(name, sw.ElapsedMilliseconds);
    };

That can be invoked with timedAction("methodname", () => lib.methodname()).

I want to do something similar for methods that return a value, but obviously Action can't be used for that purpose, since it can't return a value.

Is there a way to do this with a generic Func, so I don't have to declare one for each combination of library method parameters?

Answer 1

You can use a generic function like this:

private static TValue FuncHandler<TValue>(string name, Func<TValue> func)
{
    var sw = Stopwatch.StartNew();
    var result = func();

    trackDuration(name, sw.ElapsedMilliseconds);

    return result;
}

Call it like this:

var result = FuncHandler("name", () => MyMethod(param1));

Answer 2

Indeed, AOP will buy you more than this sort of tediousness:

https://dotnetfiddle.net/5PLCmM

// Needs to be replicated after Func<T1, TResult>, Func<T1, T2, TResult>, etc, for all the functions arities you'll want to wrap with it
public static TResult Timed<T1, /*T2, etc*/TResult>(out long duration, Func<T1, /*T2, etc*/TResult> func, T1 arg1/*T2 arg2, etc*/)
{
    //start timing
    var t0 = DateTime.Now;
    var result = func(arg1/*, arg2, etc*/);
    //end timing
    duration = (long)DateTime.Now.Subtract(t0).TotalMilliseconds;
    return result;
}

public int Factorial(int n)
{
    return n > 0 ? n * Factorial(n - 1) : 1;
}

public int Fibonacci(int n)
{
    return n > 1 ? Fibonacci(n - 2) + Fibonacci(n - 1) : n;
}

public static void Main()
{
    var program = new Program();

    long duration;

    var _12bang = Timed(out duration, program.Factorial, 12);

    Console.WriteLine("{0}! = {1} in {2} ms", 12, _12bang, duration);

    var fib31 = Timed(out duration, program.Fibonacci, 31);

    Console.WriteLine("Fib {0} = {1} in {2} ms", 31, fib31, duration);

}

(yes, I know about StopWatch; was just too lazy to put it in there)

'Hope this helps.