Populating custom array property in XAML - wpf

Question

I am trying to populate a custom string array in XAML, but am receiving an error. I subclassed a ComboBox and added a string [] that I want to fill with custom values:
public class MyComboBox : ComboBox
{
public string[] MyProperty { get { return (string[])GetValue(MyPropertyProperty); } set { SetValue(MyPropertyProperty, value); } }
public static readonly DependencyProperty MyPropertyProperty = DependencyProperty.Register("MyProperty", typeof(string[]), typeof(MyComboBox));
}
My XAML is as follows:
<Window x:Class="Samples.CustomArrayProperty"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:Samples"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Title="CustomArrayProperty" Height="300" Width="300">
<Grid>
<local:MyComboBox Height="20">
<local:MyComboBox.MyProperty>
<sys:String>Monday</sys:String>
<sys:String>Wednesday</sys:String>
<sys:String>Friday</sys:String>
</local:MyComboBox.MyProperty>
</local:MyComboBox>
</Grid>
</Window>
When I run this, I get the error: "'Monday' is not a valid value for property 'MyProperty'.".
What am I doing wrong?

Answer 1

You can create arrays in XAML using x:Array, you still need to use it as a resource like Liz's answer.
<Window.Resources>
<x:Array Type="sys:String" x:Key="days">
<sys:String>Monday</sys:String>
<sys:String>Wednesday</sys:String>
<sys:String>Friday</sys:String>
</x:Array>
</Window.Resources>
<local:MyComboBox Height="23" MyProperty="{StaticResource days}" />

Answer 2

Is there any other reason you are subclassing the ComboBox beyond what you are doing here?
Because if the idea is to just provide a list of strings to the combobox then take a look at "Add collection or array to wpf resource dictionary"
As much as possible it would be better to let the combobox take care of itself - by using the ItemsSource property. So what we are doing in the linked example is providing a 'resource' containing your list of strings, and then passing this resource to the ItemsSource as follows:
<ComboBox ItemsSource="{StaticResource stringList}" />
Define a type like this:
public class StringList : List<string> { }
And then create a static resource
<Window.Resources>
<local:StringList x:Key="stringList">
<sys:String>Monday</sys:String>
<sys:String>Wednesday</sys:String>
<sys:String>Friday</sys:String>
</local:StringList >
</Window.Resources>
I hope that helps.
Edit: You could also change your DependencyProperty to use StringList instead of String[], then your dependency property will work as well.
<local:MyComboBox MyProperty="{StaticResource stringList}" Height="23" />
And then the dependencyProperty:
public static readonly DependencyProperty MyPropertyProperty = DependencyProperty.Register("MyProperty",typeof(StringList),typeof(MyComboBox),new FrameworkPropertyMetadata(null, listChangedCallBack));
static void listChangedCallBack(DependencyObject property, DependencyPropertyChangedEventArgs args)
{
ComboBox combo = (ComboBox)property;
combo.ItemsSource= (IEnumerable)args.NewValue;
}
Then this would effectively do the same thing as binding directly to the ItemsSource. But the main thing if I understand you correctly, is just to get the Dependency property to work.

Answer 3

And, an extra example with enum:
namespace MyNamespace
{
public enum OrganizationType
{
Office365,
OnPremisses
}
}
xmlns:local="clr-namespace:MyNamespace"
<x:Array Type="local:OrganizationType" x:Key="OrganizationTypeArray">
<local:OrganizationType>Office365</local:OrganizationType>
<local:OrganizationType>OnPremisses</local:OrganizationType>
</x:Array>