Difference between 2 numbers

Question

I need the perfect algorithm or C# function to calculate the difference (distance) between 2 decimal numbers.

For example the difference between:
100

Answer 1

This is how i do it in enterprise projects:

namespace Extensions
{
    public class Functions
    {
        public static T Difference(object x1, object x2) where T : IConvertible
        {
            decimal d1 = decimal.Parse(x1.ToString());
            decimal d2 = decimal.Parse(x2.ToString());

            return (T)Convert.ChangeType(Math.Abs(d1-d2), typeof(T));
        }
    }
}

and testing:

namespace MixedTests
{
    [TestClass]
    public class ExtensionsTests
    {
        [TestMethod]
        public void Difference_int_Test()
        {
            int res2 = Functions.Difference(5, 7);
            int res3 = Functions.Difference(-3, 0);
            int res6 = Functions.Difference(-3, -9);
            int res8 = Functions.Difference(3, -5);

            Assert.AreEqual(19, res2 + res3 + res6 + res8);
        }

        [TestMethod]
        public void Difference_float_Test()
        {
            float res2_1 = Functions.Difference(5.1, 7.2);
            float res3_1 = Functions.Difference(-3.1, 0);
            double res5_9 = Functions.Difference(-3.1, -9);
            decimal res8_3 = Functions.Difference(3.1, -5.2);

            Assert.AreEqual((float)2.1, res2_1);
            Assert.AreEqual((float)3.1, res3_1);
            Assert.AreEqual(5.9, res5_9);
            Assert.AreEqual((decimal)8.3, res8_3);

        }
    }
}