How can I make a WPF combo box have the width of its widest element in XAML?

Question

I know how to do it in code, but can this be done in XAML ?

Window1.xaml:

Answer 1

I ended up with a "good enough" solution to this problem being to make the combo box never shrink below the largest size it held, similar to the old WinForms AutoSizeMode=GrowOnly.

The way I did this was with a custom value converter:

public class GrowConverter : IValueConverter
{
    public double Minimum
    {
        get;
        set;
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var dvalue = (double)value;
        if (dvalue > Minimum)
            Minimum = dvalue;
        else if (dvalue < Minimum)
            dvalue = Minimum;
        return dvalue;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

Then I configure the combo box in XAML like so:

 
        
            
        
        ...
        
    

Note that with this you need a separate instance of the GrowConverter for each combo box, unless of course you want a set of them to size together, similar to the Grid's SharedSizeScope feature.