Different type convertion behaviors in a method that returns an object using if and switch.

[johncao158]

    internal class Program
    {
        static void Main(string[] args)
        {
            var a = (int)ToValue(1, 1); // OK
            var b = (double)ToValue(1, 2); // OK
            var c = (float)ToValue(1, 3); // OK

            var a2 = (int)ToValue2(1, 1); // FAIL, Unable to cast object of type 'System.Double' to type 'System.Int32'
            var b2 = (double)ToValue2(1, 2); // OK
            var c2 = (float)ToValue2(1, 3); // FAIL, Unable to cast object of type 'System.Double' to type 'System.Single'
        }

        static object ToValue(int a, int type)
        {
            if (type == 1)
            {
                return a;
            }

            if (type == 2)
            {
                return (double)a;
            }

            if (type == 3)
            {
                return (float)a;
            }

            throw new ArgumentException();
        }

        static object ToValue2(int a, int type)
            => type switch
            {
                1 => a,
                2 => (double)a,
                3 => (float)a,
                _ => throw new ArgumentException()
            };
    }

The second method "ToValue2" will always return a "Double" value.

[HaloFour]

The switch expression can only have a single return type, which the compiler infers as double as that is the only compatible type between int, float and double. That is done separately from boxing to an object. If you want the switch expression to return a type of object, you can make the following change:

    type switch
            {
                1 => (object)a,
                2 => (double)a,
                3 => (float)a,
                _ => throw new ArgumentException()
            };