How do I use a ValueConverter with Databinding in Winforms

Question

In WPF it is easy to use a ValueConverter to format values etc, (in our case convert some numbers into a different unit, e.g km to miles)

I know it can be done in Winforms, but all my Googleing just brings up results for WPF and Silverlight.

Answer 1

You can use a TypeConverter if you're able and willing to decorate the data source property with a custom attribute.

Otherwise you have to attach to the Parse and Format events of a Binding object. This, unfortunately, eliminates using the designer for your binding for all but the simplest scenarios.

For example, let's say you wanted a TextBox bound to an integer column representing kilometers and you wanted the visual representation in miles:

In the constructor:

Binding bind = new Binding("Text", source, "PropertyName");

bind.Format += bind_Format;
bind.Parse += bind_Parse;

textBox.DataBindings.Add(bind);

...

void bind_Format(object sender, ConvertEventArgs e)
{
    int km = (int)e.Value;

    e.Value = ConvertKMToMiles(km).ToString();
}

void bind_Parse(object sender, ConvertEventArgs e)
{
    int miles = int.Parse((string)e.Value);

    e.Value = ConvertMilesToKM(miles);
}