Passing in an anonymous method/function as a parameter in C#

Question

I have a method that needs to conditionally execute a method, something like this:

int MyMethod(Func<int> someFunction)
{
    if (_someConditionIsTrue)
    {
        return someFunction;
    }

    return 0;
}

I want to be able to pass a Linq query in to MyMethod as someFunction:

int i = MyMethod(_respository.Where(u => u.Id == 1).Select(u => u.OtherId));

How do I do this?

Lasse Espeholt · Accepted Answer · 2011-04-30T07:42:07.257

6

int i = MyMethod(() => _respository.Where(u => u.Id == 1).Select(u => u.OtherId));

As you can see, I've made the query into a lambda. You will have to do this because otherwise, your query will be executed just before calling MyMethod (...and will introduce compile-time errors ;) ) and not while it executes.

A side note:

This return someFunction; should be return someFunction();.

edited Apr 30 '11 at 07:42

answered Apr 30 '11 at 07:36

Lasse Espeholt

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Doh! I almost had it this way, but I had `() = _repository` instead of `() => _respository`. This works perfectly, thanks! – Jerad Rose Apr 30 '11 at 14:49
@Jerad Rose I'm glad I could help :) – Lasse Espeholt Apr 30 '11 at 15:15

score 2 · Answer 2 · answered Apr 30 '11 at 08:33

Maybe it's a typo, but in MyMethod you need to actually call the function:

        return someFunction();

And when calling it, you're calling the function directly. Instead you need to pass a lambda expression. Also, you seem to be passing in a Func<IEnumerable<int>>; add Single(), SingleOrDefault(), First() or FirstOrDefault():

int i = MyMethod(() => _respository.Where(u => u.Id == 1).Select(u => u.OtherId).SingleOrDefault());

Passing in an anonymous method/function as a parameter in C#

2 Answers2