How to set combobox size to maximum width of its contents?

Question

I have this ComboBox

<ComboBox ItemsSource="{Binding Path=Foo.Bars}"/>

Is it possible to set the size of the drop-down list to the width of its widest element?

For example, if the contents are:

John Doe
Jane Mary
Josh

The length will be equal to the length of Jane Mary.

In addition, in this case, the content is not expected after initialization.

Answer 1

What you can do is make a converter that returns the longest length of one property of your object. You can implement such a converter as follows:

public class LongestListObjectToIntConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is IEnumerable<FooBar>)
        {
            IEnumerable<FooBar> list = (IEnumerable<FooBar>)value;

            return list.Max(bar => bar.FullName.Length);
        }

        // Default value to return
        return 100;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

And then just bind the Width property of your ComboBox, specifying the list as a Path binding and your converter as a value converter.

<Window.Resources>
    <conv:LongestListObjectToIntConverter x:Key=converter/>
</Windows.Resources>

    ...

<ComboBox ItemsSource="{Binding Path=Foo.Bars}" Width="{Binding Path=Foo.Bars, Converter={StaticResource converter}}"/>

, , ComboBox .

- , , , .

, . ValueConverters : http://www.wpftutorial.net/ValueConverters.html

Answer 2

 public class ComboBoxToMaxItemWidthConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        double maxWidth = 0;
        ComboBox cb = (ComboBox)value;
        foreach (var item in cb.Items)
        {
            ComboBoxItem cbItem = (ComboBoxItem)cb.ItemContainerGenerator.ContainerFromItem(item);
            if (cbItem.ActualWidth > maxWidth)
                maxWidth = cbItem.ActualWidth;
        }
        return maxWidth;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

<ComboBox ItemsSource="{Binding Path=Foo.Bars}" Width={Binding RelativeSource={RelativeSource Self}, Converter={StaticResource comboBoxToMaxItemWidthConverter }/>

,

Answer 3

@ArsenMkrt: cbItem null - SL ( : https://connect.microsoft.com/VisualStudio/feedback/details/687691/silverlight-4-5-beta-combobox-itemcontainergenerator-methods-return-null-and-not-a-combboxitem). .

@YogWiN: combobox ( ItemsSource), ComboBoxItem, . .

, PrepareContainerForItemOverride ComboBox, , . , MeasureOverride ...

So, as far as I know, today you cannot do this with the ComboBox control.

Answer 4

DropDownWidth can be used to set the width of the code. Use the following links for reference.

http://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.dropdownwidth%28v=VS.100%29.aspx

http://www.codeproject.com/KB/combobox/ComboBoxAutoWidth.aspx

However, this will set the size for the dropdown only.