How to disable combobox when command canExecute returns false.

Question

I have a combobox that contains a button in its template.
The button has a command attached. When canExecute returns false on that command, then the button IsEnabled is false.
I would like the IsEnabled on the whole combobox to become false in this case. I tried to do it in a trigger, but it complains because
"'IsEnabled' property cannot be set from a property trigger and appear in the trigger's condition at the same time."
How should I do this?

Answer 1

Can you post the template?

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WNC

Answer 2

For more detailed information, can you paste your full version code here?
You can use the brush like icon on the top-right of the editor.
Then I can compile your program and try to add the function or feature you have asked.

Answer 3

Here's what's in the control template:

<Border x:Name="Border" 
                        BorderThickness="1"
                            >
                        <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="Auto"/>
                        </Grid.ColumnDefinitions>
                        <Button
                              Style="{StaticResource DropDownMainButton}"
                              Name="ContentSite"
                              Command="{TemplateBinding Command}"
                              Content="{TemplateBinding Content}"
                              BorderThickness="0"
                              VerticalAlignment="Stretch"
                              VerticalContentAlignment="Stretch"
                              HorizontalAlignment="Stretch"
                              HorizontalContentAlignment="Left"
                              Margin="0"
                              Padding="0"
                              />
                        <ToggleButton Grid.Column="1" 
                              Name="ToggleButton" 
                              HorizontalAlignment="Right"
                              Template="{StaticResource DropDownToggleButton}" 
                              Margin="0"
                              Focusable="false"
                              IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}"
                              ClickMode="Press">
                        </ToggleButton>
                        <Popup 
                              Name="Popup"
                              Placement="Bottom"
                              IsOpen="{TemplateBinding IsDropDownOpen}"
                              AllowsTransparency="True" 
                              Focusable="False"
                              PopupAnimation="Slide">
                            <Grid 
                                    Name="DropDown"
                                    SnapsToDevicePixels="True"                
                                    MinWidth="{TemplateBinding ActualWidth}"
                                    MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                <Border 
                                      x:Name="DropDownBorder"
                                      Background="{StaticResource Control}"
                                      TextBlock.Foreground="{StaticResource ForeColor}"
                                      BorderThickness="1"
                                      BorderBrush="{StaticResource SolidBorderBrush}"/>
                                <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                                    <StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />
                                </ScrollViewer>
                            </Grid>
                        </Popup>
                    </Grid>
                    </Border>

Answer 4

You could write some code in the loaded event of the Button. Set the ComoBox's IsEnable the same as Button's IsEnable.

For example:

XAML

<Window x:Class="_demo.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:_demo"
    Title="Window1" Height="300" Width="300">
    <Window.CommandBindings>
        <CommandBinding Command="{x:Static local:Window1.ColorCmd}"
                    Executed="ColorCmdExecuted"
                    CanExecute="ColorCmdCanExecute"/>
    </Window.CommandBindings>
    <Grid>
        <ComboBox   x:Name="myComboBox" Margin="10,0" Height="42" VerticalAlignment="Top">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel>
                        <Button Loaded="Button_Loaded" Command="{x:Static local:Window1.ColorCmd}">
                            <Binding Path="Name"></Binding>
                        </Button>
                    </StackPanel>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>
</Window>

C#

using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
namespace _demo
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        List<MyClass> listData = new List<MyClass>();
        public static RoutedCommand ColorCmd = new RoutedCommand();
        public Window1()
        {
            InitializeComponent();
            listData.Add(new MyClass("a", "Description of a")); 
            myComboBox.ItemsSource = listData;
        }
        // ExecutedRoutedEventHandler for the custom color command.
        private void ColorCmdExecuted(object sender, ExecutedRoutedEventArgs e)
        {
        }
        // CanExecuteRoutedEventHandler for the custom color command.
        private void ColorCmdCanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = false;
        }
        private void Button_Loaded(object sender, RoutedEventArgs e)
        {
            Button btn = sender as Button;
            if (btn != null)
            {
                myComboBox.IsEnabled = btn.IsEnabled;
            }
        }
    }
    public class MyClass
    {
        public string Name { set; get; }
        public string Description { set; get; }
        public MyClass(string _name, string _des)
        {
            Name = _name;
            Description = _des;
        }
    }
}

Answer 5

The button's isEnabled is tied to a command, and the command's CanExecute changes dynamically. Will the loaded event fire every time isEnabled changes on the button?