Silverlight 4: Dispatcher-error when using Calendar or DatePicker - silverlight

Question

I read so many good answers on this site, so I never had to ask something.
Now I have a problem I cant find a answer. I'm programming a Windows App für 7.1 and try to use a Calendar Control, I dont care that much if its Calendar or DatePicker.
But whenever I change the value there, I get the following error:
"This type of Collection does not support changes to its SourceCollection from a thread different from the Dispatcher thread."
Since im quite beginner, I dont do anything fancy with Threads and I didnt find anything about this error in the web, so I guess, this must be a unique error at my environment.
Has anyone a idea, where this error can come from?
Thanks for your responses
Müller Matthias

Answer 1

You should use DatePicker from SDK namespace,
http://samples.msdn.microsoft.com/silverlight/samplebrowser/#/?sref=System.Windows.Controls.Calendar
I can also suggest Telerik's silverlight controls
http://demos.telerik.com/silverlight/
<UserControl xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk" x:Class="CalendarExample.Page"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
FontFamily="Trebuchet MS" FontSize="11"
Width="600" Height="750">
<StackPanel x:Name="LayoutRoot" Background="White">
<StackPanel Orientation="Horizontal" Margin="5" >
<!-- A basic Calendar. -->
<TextBlock Width="100"
Text="Calendar with date ranges defined:" TextWrapping="Wrap" Margin="5" />
<sdk:Calendar x:Name="cal" />
<!-- A Calendar does not highlight today's date. -->
<TextBlock Width="100"
Text="Calendar that does not highlight today's date:" TextWrapping="Wrap" Margin="5"/>
<sdk:Calendar x:Name="cal2" Canvas.Left="270" Canvas.Top="100"
IsTodayHighlighted="false" />
</StackPanel>
<!-- Two DatePicker controls, one using the default Short date format -->
<!-- and the other using the Long date format. -->
<StackPanel Orientation="Horizontal" >
<TextBlock Width="200" Margin="5"
Text="DatePicker with Short date format and Calendar event handlers:" TextWrapping="Wrap" />
<sdk:DatePicker x:Name="dp1" Height="20" Width="200" />
</StackPanel>
<StackPanel Orientation="Horizontal" >
<TextBlock Width="200" Margin="5"
Text="DatePicker with Long date format and DateSelected event handler:" TextWrapping="Wrap" />
<sdk:DatePicker Height="20" x:Name="dp2" SelectedDateFormat="Long" Width="200"/>
</StackPanel>
<!-- Output TextBlock -->
<TextBlock x:Name="text1" HorizontalAlignment="Left" Height="40" Width="350" Margin="5" />
<!-- A Calendar to demonstrate multiple selection. -->
<StackPanel Orientation="Horizontal" >
<TextBlock Width="200" Margin="5"
Text="Calendar with multiple selections and blackout dates:" TextWrapping="Wrap" />
<sdk:Calendar x:Name="cal3" />
</StackPanel>
</StackPanel>