Math errors in custom control

[Mikey_H]

Control code:

public class MathTester : Control, INotifyPropertyChanged
{
public static DependencyProperty ValueProperty =
DependencyProperty.Register("Value",
typeof(double), typeof(MathTester),
new PropertyMetadata(OnValuePropertyChanged));

    public static DependencyProperty DivisorProperty =
        DependencyProperty.Register("Divisor",
        typeof(double), typeof(MathTester),
        new PropertyMetadata(OnDivisorPropertyChanged));

    public static DependencyProperty ResultProperty =
        DependencyProperty.Register("Result",
        typeof(double), typeof(MathTester),
        new PropertyMetadata(OnResultPropertyChanged));

    public static DependencyProperty DecimalsProperty =
        DependencyProperty.Register("Decimals",
        typeof(int), typeof(MathTester),
        new PropertyMetadata(15, OnDecimalsPropertyChanged));

    public static DependencyProperty RoundProperty =
        DependencyProperty.Register("Round",
        typeof(bool), typeof(MathTester),
        new PropertyMetadata(false, OnRoundPropertyChanged));

    public double Value
    {
        get { return (double)GetValue(ValueProperty); }
        set { SetValue(ValueProperty, value); }
    }

    public double Divisor
    {
        get { return (double)GetValue(DivisorProperty); }
        set { SetValue(DivisorProperty, value); }
    }

    public double Result
    {
        get { return (double)GetValue(ResultProperty); }
        set { SetValue(ResultProperty, value); }
    }

    public int Decimals
    {
        get { return (int)GetValue(DecimalsProperty); }
        set { SetValue(DecimalsProperty, value); }
    }

    public bool Round
    {
        get { return (bool)GetValue(RoundProperty); }
        set { SetValue(RoundProperty, value); }
    }

    static MathTester()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(MathTester), 
            new FrameworkPropertyMetadata(typeof(MathTester)));
    }

    public MathTester()
    {
        Divide();
    }

    private void Divide()
    {
        if (Value != 0 && Divisor != 0)
            if (Round == true && Decimals > 0 && Decimals < 16)
                Result = Math.Round(Value / Diviso

[Mark Salsbery]

This gets discussed often, sometimes passionately when the discussion involves someone who absolutely can't believe a simple calculation like 1.2/0.1 can't be exactly represented in a double precision floating point number format. Floating point numbers are only approximations, since there is a finite number of bits to represent an infinite number of - numbers. A couple links of possible interest... What Every Computer Scientist Should Know About Floating-Point Arithmetic[^] Joe Newcomer's Floating Point Explorer[^]

Mark Salsbery Microsoft MVP - Visual C++ :java: