Func and Cannot implicitly convert type

So I have simple example of my code and I can't find idea how to rewrite it. Code:

 class Program
  {
    static void Main(string[] args)
    {
      var cat = new Cat();
      cat
        .ToFeed(arg => LikeMilk(1), c => c.I开发者_Go百科nc())
        .ToFeed(arg => LikeMilk(2), c => c.Inc());
    }

    private static bool LikeMilk(int liters)
    {
      return liters <1;
    }
  }

  public class Cat
  {
    private int Weith { get; set; }

    public void Inc()
    {
      Weith++;
    }

    public Cat ToFeed(Func<int, bool> predicate, Action<Cat> action)
    {
      if (predicate)  // Error: Cannot implicitly convert type 'System.Func<int,bool>' to 'bool' 
        action(this);
      return this;
    }
  }
}

Of course I can change signature ToFeed to ToFeed(bool predicate, Action<Cat> action), but I don't want to do it. I understand that I have to add int parameter to call of predicate, but I have added it in Main()

How can I solve this problem?

Thanks

I believe your method should be something like this:

public Cat ToFeed(Func<int, bool> predicate, Action<Cat> action)
{
  if (predicate(Weith)) // By the way, it is properly the word Weight you're looking for :)
    action(this);
  return this;
}

predicate(Weith) executes the function predicate with the value of the property Weith. A Func<int, bool> is not in itself a bool (true/false - which is what an if-sentence expects.) However, it´s something you can execute, with an int as argument, to obtain a bool, therefore you need (arguments).

Updated:

I'm not entirely sure of what you want. But you could do as you say yourself and use a bool instead of a Func<*>. And if you want your evaluation of LikeMilk to be delayed, you can say like this:

public Cat ToFeed(Func<bool> predicate, Action<Cat> action)
{
  if (predicate())
     action(this);
  return this;
}

and

var cat = new Cat().ToFeed(() => LikeMilk(1), c => c.Inc())
                   .ToFeed(() => LikeMilk(2), c => c.Inc());

But that doesn't make much sense because your method LikeMilk will return the same thing delay-executed or not.

You're passing a function value to 'ToFeed' and not a bool value. That's why you need to actually invoke the function:

if (predicate(this.liters))   //Check whether cat still wants milk. Yum!
    action(this);

Edit: Now that I look closer at your code, I see that you hard coded the amount of liters in the main function and that thus the lambda-parameter arg is useless.

You should change the code in your main method to:

var cat = new Cat();
      cat
        .ToFeed(arg => LikeMilk(arg), c => c.Inc())
        .ToFeed(arg => LikeMilk(arg), c => c.Inc());

Now the lambda actually uses the parameter passed. Then you can add a liters-Variable to your Cat-class which you pass to the predicate. See my updated code above.

You send result of delegate call instead of the delegate, try this version of your code

class Program
      {
        static void Main(string[] args)
        {
          var cat = new Cat();
          cat
            .ToFeed(1, LikeMilk, c.Inc)
            .ToFeed(2, LikeMilk, c.Inc);
        }

        private static bool LikeMilk(int liters)
        {
          return liters < 1;
        }
      }

      public class Cat
      {
        private int Weith { get; set; }

        public void Inc()
        {
          Weith++;
        }

        public Cat ToFeed(int liters, Func<int, bool> predicate, Action<Cat> action)
        {
          if (predicate(liters))
            action(this);
          return this;
        }
      }
    }