IsMultiple

gistfile1.cs

[Test]
public void IsMultipleTests()
{
    // true
    Console.WriteLine(IsMultiple(0.0075, 0.0001));
    Console.WriteLine(IsMultiple(500.4, 0.001));
    Console.WriteLine(IsMultiple(500.4, 0.0001));
    Console.WriteLine(IsMultiple(500.4, 0.00001));
    Console.WriteLine(IsMultiple(500.4, 0.000001));
    Console.WriteLine(IsMultiple(500.4, 0.0000001));
    Console.WriteLine(IsMultiple(500.4, 0.00000001));
    Console.WriteLine(IsMultiple(500.4, 0.000000001));
    Console.WriteLine(IsMultiple(500.4, 0.0000000001));
    Console.WriteLine(IsMultiple(500.4, 0.00000000001));

    // false
    Console.WriteLine(IsMultiple(500.4, 0.0000007));
    Console.WriteLine(IsMultiple(500.4, 0.0021));
    Console.WriteLine(IsMultiple(0.00751, 0.0001));
}

private static bool IsMultiple(double value, double multipleOf)
{
    const double epsilon = 2.2204460492503131e-016;
    const double tolerance = epsilon*300; // this tolerance seems too big

    double remainder = value%multipleOf;
    double absRemainder = Math.Abs(remainder);

    if (absRemainder < tolerance)
    {
        return true;
    }
    if (Math.Abs(multipleOf) - absRemainder < tolerance)
    {
        return true;
    }

    return false;
}