Overloading A Generic Method

Question

User1231829591 posted

Hi all, currently I have the following generic method which takes two parameters of the same type:

public T AddNumbers<T>(T a, T b)
        {
            dynamic num1 = a;
            dynamic num2 = b;
            return num1 + num2;
        }

I would like to overload the method above so that it will take two parameters of differing types. I have tried the following but it does not work.

public T AddNumbers<S,T>(S a, T b)
        {
            dynamic num1 = a;
            dynamic num2 = b;
            return num1 + num2;
        }

I get the following errors

The call is ambiguous between the following methods or properties: 'AddNumbers<int>(int, int)' and 'AddNumbers<int,int>(int, int)'

The call is ambiguous between the following methods or properties: 'AddNumbers<double>(double, double)' and 'AddNumbers<double,double>(double, double)'

Thanks in advance.

Answer 1

User2103319870 posted

ManyTitles

The call is ambiguous between the following methods or properties: 'AddNumbers<int>(int, int)' and 'AddNumbers<int,int>(int, int)' The call is ambiguous between the following methods or properties: 'AddNumbers<double>(double, double)' and 'AddNumbers<double,double>(double, double)'

Try calling the method by passing the datatype value like below

 Test objtext = new Test();
                int t1 = objtext.AddNumbers<int>(1, 2);
                double t2 = objtext.AddNumbers<double,double>(1, 2);

• Sample Working Demo

Answer 2

User1574164112 posted

These all worked for me without any errors. 

        protected void Button1_Click(object sender, EventArgs e)
        {
            var x = AddNumbers<int>(2, 9);

            var a = AddNumbers<int,double>(2, 9.0);

            var b = AddNumbers<int, int>(2, 2);

            var c = AddNumbers<double, double>(9.0, 9.0);

        }

The only thing I had to make sure was that the the return type was compatible with the calculation.  e,g this would not work because adding a double and an int returns a double but the second parameter is the type (int) that is returned.

var a = AddNumbers<double, int >(9.0, 2);

I was using .Net 4.5, what version are you using?

Answer 3

User1574164112 posted

As a2h says, make sure you specify the data types

This will give a ambiguous error

var a = AddNumbers(2, 2);

Answer 4

User1231829591 posted

Hi all, I thought that by overloading a generic function I can overload a delegate simply by passing the overloaded method's name to it (the delegate) but I get the errors I posted above. So my question is can I even use overloaded methods with delegates.

Answer 5

User614698185 posted

Hi ManyTitles,

This is about overloaded methods pass value to delegates:

static void Main(string[] args)
{
    D1 d = new D1(M1);
    d();
    Console.Read();
}
public delegate void D1();

public static void M1()
{
    Console.WriteLine("M1");
}

public static void M1(int p1)
{
    Console.WriteLine("M1 with p1");
}

This is about overloaded Generic methods pass value to Generic delegates:

public static void Main()
{
    D1<int> d = new D1<int>(M1<int>);
    d();
    Console.Read();
}

public delegate void D1<T>();

public static void M1<T>()
{
    Console.WriteLine("M1");
}

public static void M1<T>(T p1)
{
    Console.WriteLine("M1 with p1");
} 

The above codes are right usage. Incorrect usage usually violate this principle ambiguity. If you write a program even if the compiler does not know how to execute it, it will  certainly be an error.

Best Regards,

Candice Zhou