Question

I create a own ComboBoxItem. Here I have simplified the code. The ComboBoxItem contain a CheckBox.

ComboBoxItem Control xaml:

<ComboBoxItem x:Class="WpfApplication1.MyCombobox"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Height="50"
             Width="200">
    <!-- ... -->
    <StackPanel>
        <CheckBox IsChecked="{Binding Path=IsCheckboxChecked}" IsEnabled="{Binding Path=IsCheckboxEnabled}">
            <CheckBox.LayoutTransform>
                <ScaleTransform ScaleX="1" ScaleY="1" />
            </CheckBox.LayoutTransform>
        </CheckBox>
        <!-- ... -->
    </StackPanel>
</ComboBoxItem>

ComboBoxItem Control c# (code behind)

public partial class MyCombobox
{
    public MyCombobox()
    {
        InitializeComponent();
        DataContext = this;

        //Defaults
        IsCheckboxChecked = false;
        IsCheckboxEnabled = true;

        //...
    }

    //...

    public string Text { get; set; }

    public bool IsCheckboxChecked { get; set; }

    public bool IsCheckboxEnabled { get; set; }

    //...
}

and I include it so:

<WpfApplication1:MyCombobox IsCheckboxChecked="{Binding Path=IsMyCheckBoxChecked, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" IsCheckboxEnabled="{Binding Path=IsMyCheckBoxEnabled, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" Text="Write your Text here" />

When I run my application I get this error:

A fatal error occurred: a ‘Binding’ cannot be set on the
‘IsCheckboxChecked’ property of type ‘MyCombobox’. A ‘Binding’ can
only be set on a Dependency Property of a DependencyObject

What do I make wrong?

Answer 1

well the error is pretty clear: You have to make a DP of your IsCheckboxChecked field:

public static readonly DependencyProperty IsCheckboxCheckedProperty = DependencyProperty.Register("IsCheckboxChecked", typeof(bool), typeof(MyComboBox));
public bool IsCheckboxChecked
{
    get { return (bool)GetValue(IsCheckboxCheckedProperty); }
    set { SetValue(IsCheckboxCheckedProperty, value); }
}

instead of:

public bool IsCheckboxChecked { get; set; }

but this also means you’d have to make your MycomboBox class inherit the DependencyObject class:

public partial class MyCombobox : DependencyObject

I suggest this: http://msdn.microsoft.com/en-gb/library/ms752347.aspx