I have implemented my own usercontrol based on listboxes. It has a dependency property with type of a collection. It works fine when I have only one instance of the usercontrol in a window, but if I have multiple instances I get problem that they share the collection dependency property. Below is a sample illustrating this.
My user control called SimpleList:
<UserControl x:Class="ItemsTest.SimpleList"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Name="_simpleList">
<StackPanel>
<TextBlock Text="{Binding Path=Title, ElementName=_simpleList}" />
<ListBox
ItemsSource="{Binding Path=Numbers, ElementName=_simpleList}">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
</StackPanel>
</UserControl>
Code behind:
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
namespace ItemsTest
{
public partial class SimpleList : UserControl
{
public SimpleList()
{
InitializeComponent();
}
public string Title
{
get { return (string)GetValue(TitleProperty); }
set { SetValue(TitleProperty, value); }
}
public static readonly DependencyProperty TitleProperty =
DependencyProperty.Register("Title", typeof(string), typeof(SimpleList), new UIPropertyMetadata(""));
public List<int> Numbers
{
get { return (List<int> )GetValue(NumbersProperty); }
set { SetValue(NumbersProperty, value); }
}
public static readonly DependencyProperty NumbersProperty =
DependencyProperty.Register("Numbers ", typeof(List<int>), typeof(SimpleList), new UIPropertyMetadata(new List<int>()));
}
}
I use like this:
<StackPanel>
<ItemsTest:SimpleList Title="First">
<ItemsTest:SimpleList.Numbers>
<sys:Int32>1</sys:Int32>
<sys:Int32>2</sys:Int32>
<sys:Int32>3</sys:Int32>
</ItemsTest:SimpleList.Numbers>
</ItemsTest:SimpleList>
<ItemsTest:SimpleList Title="Second">
<ItemsTest:SimpleList.Numbers>
<sys:Int32>4</sys:Int32>
<sys:Int32>5</sys:Int32>
<sys:Int32>6</sys:Int32>
</ItemsTest:SimpleList.Numbers>
</ItemsTest:SimpleList>
</StackPanel>
I expect the following to show up in my window:
First
123
Second
456
But what I see is:
First
123456
Second
123456
How do I get multiple SimpleList not to share their Numbers Collection???
Found the answer, the constructor needs to initialize the property instead of letting the static property do itself:
public SimpleList()
{
SetValue(NumbersProperty, new List<int>());
InitializeComponent();
}
Collection-Type Dependency Properties
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