How to hide combobox toggle button if there is only one item? - wpf

Question

I have a WPF application. In one window there is a combobox..and I want to hide the toggle button and disable the combo box if there is only one item.
How would I achieve this ?
I have tried the below code for hiding the toggle button. But of no luck
Any help would be appreciated. thanks
<ComboBox x:Name="CList" ItemsSource="{Binding Path=C}" >
<Style TargetType="{x:Type ToggleButton}" >
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Items.Count, ElementName=CList}" Value="1">
<Setter Property="Visibility" Value="Hidden" />
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox>

Answer 1

The better solution is to replace the template of combo box with a control template(which only contain textblock) when the item count is zero.
Here is the xaml for the same.
<ComboBox Name="CList" ItemsSource="{Binding Path=C}"
SelectedItem="{Binding Path=CC}" VerticalAlignment="Center" Margin="0,0,10,0" >
<ComboBox.Style>
<Style TargetType="{x:Type ComboBox}" >
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Items.Count, ElementName=CList}" Value="1">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<TextBlock Text="{Binding Items[0], ElementName=CList}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ComboBox.Style>
</ComboBox>

Answer 2

You would need to change the Template of the ComboBox and implement the trigger inside that. You have no access to the controls in the template from the outside.
(You could copy and modify the existing template, directly modifying a part of the template is practically impossible)

Answer 3

You can always use a Converter also:
(Sorry I didn't fully read your question)
Converters
using System;
using System.Windows;
using System.Windows.Data;
using System.Globalization;
namespace WPFSandbox
{
public class ComboBoxItemCountToEnabledConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value != null && value.GetType() == typeof(Int32))
{
if ((int)value > 1)
return true;
}
return false;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
public class ComboBoxItemCountToVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value != null && value.GetType() == typeof(Int32))
{
if ((int)value > 1)
return Visibility.Visible;
}
return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
XAML
<Window
...
...
xmlns:converters="clr-namespace:WPFSandbox">
<Window.Resources>
<converters:ComboBoxItemCountToVisibilityConverter x:Key="ComboBoxItemCountToVisibilityConverter"/>
<converters:ComboBoxItemCountToEnabledConverter x:Key="ComboBoxItemCountToEnabledConverter"/>
</Window.Resources>
<StackPanel>
<ComboBox ItemsSource="{Binding C}" IsEnabled="{Binding Path=C.Count, Converter={StaticResource ComboBoxItemCountToEnabledConverter}}"/>
<ToggleButton Visibility="{Binding Path=C.Count, Converter={StaticResource ComboBoxItemCountToVisibilityConverter}}"/>
</StackPanel>