Ok I am getting sick of this problem.
I am trying to make UserControl where I can populate its content from XAML. Previously I have created ObservableCollection DependencyProperty. It was working at runtime but at design time there was an error:
Object reference not set to an instance of an object.
Now I did simpler version:
public partial class UC : UserControl
{
public UC()
{
Labels = new ObservableCollection<Label>();
InitializeComponent();
Labels.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(Labels_CollectionChanged);
}
void Labels_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
foreach (Label uc in e.NewItems)
Container.Children.Add(uc);
}
private ObservableCollection<Label> _lables = new ObservableCollection<Label>();
public ObservableCollection<Label> Labels
{
get { return _lables; }
set { _lables = value; }
}
}
This is how I like to use my UserControll
<Window x:Class="WpfApplication1.MainWindow"
xmlns:gsh="clr-namespace:WpfApplication1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid Margin="0,0,0,30">
<gsh:UC x:Name="uC1">
<gsh:UC.Labels>
<Label Content="qwerty1" />
<Label Content="qwerty2" />
</gsh:UC.Labels>
</gsh:UC>
</Grid>
However it still gives me the error at design time:
Object reference not set to an instance of an object.
So if anyone can help me please.
How can I make UserControl that I can use like native controls which I can populate with collection of elements? I am trying to find the answer second day already.
I usually check to see if i am in design time before wiring up events etc..
It could be that your Container is null in design mode.
public class Utils
{
public static bool IsInDesignerMode
{
get
{
return ((bool)(DesignerProperties.IsInDesignModeProperty
.GetMetadata(typeof(DependencyObject)).DefaultValue));
}
}
}
Maybe in your constructor you should do this..
public UC()
{
InitializeComponent();
if (!Utils.IsInDesignerMode)
{
Labels = new ObservableCollection<Label>();
Labels.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(Labels_CollectionChanged);
}
}
On another note though i think you would be better using an ItemsControl