CODEWITHSUNDEEP
c#genericsoverloading
user2146414
user2146414

Reputation: 1038

Call overloaded generic method from generic method

My question is: Why is AddData(string data) never called? When I call ds.Add("Some text") then the type of data parameter is known at compilation time thus the overloaded implementation of Add should call AddData(string) method (or this is what I was hoped for)

The output is

Ignore data of type System.String
Ignore data of type System.Double

using System;

namespace GenericCall
{
    interface IDataStore
    {
        void Add<T>(T data);
    }

    class MyDataStore : IDataStore
    {
        public void Add<T>(T data)
        {
            AddData(data);
        }

        private void AddData<T>(T data)
        {
            Console.WriteLine($"Ignore data of type {data.GetType()}");
        }

        private void AddData(string data)
        {
            Console.WriteLine("Accept string data");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            MyDataStore ds = new MyDataStore();
            ds.Add("Some text");
            ds.Add(3.14);
        }
    }
}

Upvotes: 0

Views: 120

Answers (1)

Sweeper
Sweeper

Reputation: 274520

Overload resolution happens at compile time for your code.

At compile time, the compiler has no knowledge of what T actually is, so this call:

public void Add<T>(T data)
{
    AddData(data); <------
}

can only be resolved to the generic AddData, according to the rules of overload resolution.

One way to make overload resolution happen at runtime is to make the public Add accept a dynamic parameter:

// you should change the interface declaration also!
public void Add(dynamic data)
{
    AddData(data);
}

This will produce the output:

Accept string data
Ignore data of type System.Double

Upvotes: 1

Related Questions