Question

i try to generate some codes. i face to face delegates. Everythings is ok.(Look below) But appearing a warning: you shold assing value why? but second code below is ok.

namespace Delegates
{
    class Program
    {
        static void Main(string[] args)
        {


        HesapMak hesapla = new HesapMak();
        hesapla.Calculator = new HesapMak.Hesap(hesapla.Sum);

        double sonuc = hesapla.Calculator(34, 2);
        Console.WriteLine("Toplama Sonucu:{0}",sonuc.ToString());
        Console.ReadKey();
    }
}

class HesapMak
{
   public double Sum(double s1, double s2)
    {
        return s1 + s2;
    }

   public double Cikarma(double s1, double s2)
    {
        return s1 - s2;
    }

   public double Multiply(double s1, double s2)
    {
        return s1 * s2;
    }
   public double Divide(double s1, double s2)
    {
        return s1 / s2;
    }
      public delegate double Hesap(double s1, double s2);
      public Hesap Calculator; ----< they want me assingn value

}

}
namespace Delegates

{

    class Program

    {

        static void Main(string[] args)

        {

            HesapMak hesapla = new HesapMak();

            hesapla.Calculator = new HesapMak.Hesap(hesapla.Sum);
            double sonuc = hesapla.Calculator(34, 2);

            Console.WriteLine("Toplama Sonucu:{0}",sonuc.ToString());

            Console.ReadKey();

        }

    }
    class HesapMak

    {

       public double Sum(double s1, double s2)

        {

            return s1 + s2;

        }
       public double Cikarma(double s1, double s2)

        {

            return s1 - s2;

        }
       public double Multiply(double s1, double s2)

        {

            return s1 * s2;

        }

       public double Divide(double s1, double s2)

        {

            return s1 / s2;

        }

          public delegate double Hesap(double s1, double s2);

          public Hesap Calculator=null;

    }
}
												

Answer 1

This is not neccessary and should not result in a warning.
Section 10.4.4 of the C# (3.0) spec says:

The initial value of a field, whether it be a static field or an instance field, is the default value (Section 5.2) of the field’s type. It is not possible to observe the value of a field before this default initialization has occurred, and a field is thus never "uninitialized".
The following categories of variables are automatically initialized to their default values:

Section 5.2 of the C# (3.0) spec says:

The default value of a variable depends on the type of the variable and is determined as follows:

• For a variable of a value-type, the default value is the same as the value computed by the value-type’s default constructor (Section 4.1.1).
• For a variable of a reference-type, the default value is null.

So public Hesap Calculator; is initialized automatically to its default value (null).