WPF Bind Checkbox IsChecked to other Checkboxes (IsChecked || !IsEnabled)

Question

I have a select 'All' checkbox that I would like to be bound to the (IsChecked || !IsEnabled) of other checkboxes.

• Checking 'All' checks all enabled checkboxes.

• Unchecking 'All' unchecks all checkboxes.

• Manually checking each enabled checkbox will check 'All'.

• When all enabled checkboxes and 'All' are checked and user unchecks any checkbox, 'All' automatically unchecks.

I am new to WPF Databinding. I was thinking maybe I just handle the click of 'All' to set the other checkboxes. But I don't know how to bind to both properties of multiple sources. When I click 'All' and manually uncheck another checkbox, 'All' needs to uncheck.

Joe

Answer 1

Here's a way to do it in Xaml with Converters. This is assuming that all your CheckBox's are added directly as Controls in Xaml (it's not very dynamic, won't work for DataTemplate's etc). First we create three CheckBoxes (CheckBox1, CheckBox2, CheckBox3) that will be Checked/Unchecked when Checking the CheckAllCheckBox. It will also work in reverse.

Update
The last part (ignore disabled CheckBox) was a bit of a problem here and I'm not crazy about this solution but I can't see a better way. We store the values from Convert and re-use them in ConvertBack for the disabled CheckBox's. Doing this, we should also add the x:Shared="False" attribute for the CheckAllConverter since a new instance is required for every MultiBinding that would use it (unlikely in this case but still..)

<Window.Resources>
    <local:CheckAllConverter x:Key="CheckAllConverter" x:Shared="False"/>
</Window.Resources>
<StackPanel>
    <CheckBox Content="Check All"
              Name="CheckAllCheckBox">
        <CheckBox.IsChecked>
            <MultiBinding Converter="{StaticResource CheckAllConverter}">
                <Binding ElementName="CheckBox1" Path="IsChecked" />
                <Binding ElementName="CheckBox1" Path="IsEnabled" Mode="OneWay"/>
                <Binding ElementName="CheckBox2" Path="IsChecked" />
                <Binding ElementName="CheckBox2" Path="IsEnabled" Mode="OneWay"/>
                <Binding ElementName="CheckBox3" Path="IsChecked" />
                <Binding ElementName="CheckBox3" Path="IsEnabled" Mode="OneWay"/>
            </MultiBinding>
        </CheckBox.IsChecked>
    </CheckBox>
    <CheckBox Content="CheckBox 1"
              Name="CheckBox1"/>
    <CheckBox Content="CheckBox 2"
              Name="CheckBox2"/>
    <CheckBox Content="CheckBox 3"
              Name="CheckBox3"/>
</StackPanel>

The Converter for CheckAll

public class CheckAllConverter : IMultiValueConverter
{
    private object[] convertValues = null;
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        convertValues = new object[values.Length];
        for(int i = 0; i < values.Length; i++)
        {
            convertValues[i] = values[i];
        }

        for (int i = 0; i < values.Length; i += 2)
        {
            bool isChecked = (bool)values[i];
            bool isEnabled = (bool)values[i + 1];
            if (isEnabled == false)
            {
                continue;
            }
            if (isChecked == false)
            {
                return false;
            }
        }
        return true;
    }
    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        object[] values = new object[targetTypes.Length];
        for (int i = 0; i < values.Length; i += 2)
        {
            if (convertValues != null && (bool)convertValues[i + 1] == false)
            {
                values[i] = convertValues[i];
            }
            else
            {
                values[i] = value;
            }
            // IsEnabled is OneWay and won't care about this value
            values[i + 1] = null;
        }
        return values;
    }
}

Taconite

This is great. I didn't need the uncheck checkbox or the other converter and I removed the trigger to disable. However, I would like to allow the other checkboxes to be able to be disabled. They shouldn't become checked when disabled but they won't count against the check all. For example. If Checkbox 2 is disabled, clicking Check All won't check it. And if I Checkbox1/3 are checked, Check All becomes checked. – Joe

Yes, that's what I thought :) One checkbox should do it since it works both ways, I missread the question. I'll update my answer and look at into your comments – Taconite

Thanks! I started playing with what you gave. I made it messy by making a one way binding to the IsEnabled property. When converting an unchecked checkbox I check i+1 for the oneway enabled property heh. Its messy and I didn't see a way to ignored disabled checkboxes when converting back. I'm curious to see your proposed solution. – Joe

@Thx: We were doing exactly the same thing :) Since the Binding is OneWay we can send whatever we want for the odd parameters e.g. null – Taconite

@Thx: Wait, you're right. I doesn't work yet.. Checking CheckAll checks disabled CheckBoxes. Gonna give it another try – Taconite

@Thx: Updated again, hopefully it will be complete this time :) – Taconite

Sneaky :D. It works. I will also look into a one way binding to check / decheck the 'All' checkbox. Upon clicking it it would loop through the checkboxes, and check/uncheck them if they are enabled. I will maintain a list of checkboxes to 'subscribe' to to raise an event to one property. It might be a little more elegant. – Joe

@Thx: Hehe yes, it might :) Good luck! – Taconite

Answer 2

I'd create a ViewModel behind your View class using the MVVM design pattern: http://msdn.microsoft.com/en-us/magazine/dd419663.aspx

Then on your ViewModel (which will have to implement INotifyPropertyChanged) you can have multiple bool properties, one for each CheckBox and another for all of them:

public bool IsChecked1
{
    get
    {
         return isChecked1;
    }
    set
    {
         if (isChecked1 != value)
         {
             isChecked1 = value;
             RaisePropertyChanged("IsChecked1");
             RaisePropertyChanged("AreAllChecked");
         }
    }
}

// And so on

public bool AreAllChecked
{
    get
    {
        return IsChecked1 && IsChecked2; // etc.
    }   
    set
    {
        if (AreAllChecked != value)
        {
            IsChecked1 = value;
            IsChecked2 = value;
            // etc.
        }
    }
}  

Psychomotor