Could you describe what generic type inference is and what will be the output of this program?

    class Program
    {
        static void SomeMethod(object parameter)
        {
            Console.WriteLine("Hello");
        }

        static void SomeMethod<T>(T parameter)
        {
            Console.WriteLine("World");
        }

        static void Main(string[] args)
        {
            object obj = "x";
            string s = "x";
            SomeMethod(obj);
            SomeMethod(s);
        }
    }
}

Experience Level: Senior
Tags: .NET C# Code challenge

Answer

Answer

The method overload is chosen by parameter matching and in the first call to SomeMethod, the object passed to the method is of type object. For that reason the overload with object parameter is used and "Hello" is sent to the console.

In the second call to SomeMethod the object passed to the method is of type string. The generic type T is inferred from the string parameter and for that reason the overload with T parameter is used and "World" is sent to the console.

So the final output will be the following:

Hello
World

It's quite useful to know about generic type inferrence. See the links below to read more about how it can be used in the real world to simplify your code.

Links

Read these great articles:

Related C# job interview questions
.NET challenge
.NET challenge

Are you learning C#? Try our test we designed to help you progress faster.

Test yourself