Question

I am writing a table driven method in C#. I have a dictionary of this signature:

Diction<Func<string, bool>, Func<string>>

So it will take a string as a parameter and let me execute a method which returns a bool on the string (eg string.Length > 5). The value corresponds to methods which return a string.

But the method which does this takes a func as a parameter. I want to change this so it takes a string but then it looks at the string’s length and gets the right value from the dictionary.

Something like this:

dict[s.Length]; Or dict[s]; // Where s is a string

If it is greater than 5, it gets the Func which runs the method for the length > 5, otherwise it gets another func. I want to avoid using if/else as this is an exercise in coming out of that habit.

I could use ?: but this is only for two conditions. The main thing is this is for an API and I want the user of the API to just pass in the string as a parameter, and then look at the length and get the right func from the dictionary.

How best should I go about this?
Thanks

Answer 1

So it looks like you’re really just using the dictionary as a set of key-value pairs and you want to evaluate the “value” function for the first “key” predicate that returns true. Rather than a Dictionary (since you’re not really doing a lookup), I would use an array (anonymous here for convenience):

var map = new [] {
    new {
        Predicate = new Func<string, bool>(s => s.Length < 5),
        Selector = new Func<string, string>(s => s + " is short.")
    },
    new {
        Predicate = new Func<string, bool>(s => true),
        Selector = new Func<string, string>(s => s + " is long.")
    }
};

var input = "Long String";
var result = map.First(x => x.Predicate(input)).Selector(input);