Question

I have a ForEachWithIndex EM

static void ForEachWithIndex<T>(this IEnumerable<T> enu, Action<T, int> action)
{
    int i = 0;
    foreach(T item in enu)
        action(item, i++);
}

I call it like this

my_int_array.ForEachWithIndex((x, i) => x += i);

Now i want to create one which checks for condition and then perform that action.

Usually i use above as

my_int_array.ForEachWithIndex((x,i) => 
{
    if (x != 0)
        x += i;
});

I want a EM that takes that condition as parameter also. How to do that?

Answer 1

You need to pass an additional Func parameter, something like this:

public static void ForEachWithIndex<T>(this IEnumerable<T> enu,
                           Action<T, int> action, Func<T, int, bool> condition)
{
    int i = 0;
    foreach (T item in enu)
    {
        if (condition(item, i))
        {
            action(item, i);
        }
        ++i;
    }
}

And this is what the code for your example look like:

my_int_array.ForEachWithIndex((x, i) => x += i, (x, i) => x != 0);