Home > Posts > Fix: The tag ‘TimeUpDown’ does not exist in XML namespace (Silverlight Toolkit)

Fix: The tag ‘TimeUpDown’ does not exist in XML namespace (Silverlight Toolkit)

If you use TimeUpDown control from Silverlight Toolkit in your XAML like below (copy pasting from CaptionGrid at ClipFlair source):

<DataTemplate x:Key="StartTimeCellTemplate">
<TextBlock Margin="4" Text="{Binding Begin}" />

<DataTemplate x:Key="StartTimeCellEditTemplate">
<input:TimeUpDown Format="hh:mm:ss"
Value="{Binding Begin, Mode=TwoWay, ValidatesOnExceptions=True, NotifyOnValidationError=true}"



then even though it seems to not complain in the XAML designer of Visual Studio 2010, then at Build time, even if you’ve added a reference to System.Windows.Controls.Input.Toolkit assembly (the version for the Silverlight 5 Toolkit [December 2011 release]), you get:

The tag ‘TimeUpDown’ does not exist in XML namespace ‘clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Input.Toolkit’


Similar bad behaviour occurs if you try to drag-drop the TimeUpDown control from Visual Studio toolbar (assuming you’ve installed the Silverlight Toolkit first) onto the XAML designer, no xml namespace (named xmlns:input above) is added and you just get <TimeUpDown /> in the designer.


The solution is to also add to your project a reference to System.Windows.Controls assembly (be sure to select same version DLL as above [e.g.]). For some reason the System.Windows.Controls.Input.Toolkit doesn’t seem to pull that together and must have some internal dependency to it (although the error you get is very cryptic).

Below is the Add Reference dialog of Visual Studio 2010, you either use the “Extensions” from the right handside, or type-in “System.Windows.Controls” at the search box to quickly spot those two assemblies.



Note that If you have a Silverlight assembly project with some UserControl in it and you apply the workaround I mentioned above, then if you use that UserControl in a Silverlight app (in a Page or other UserControl) you get a RUNTIME error this time at launch saying XamlParserError at the title bar and the exception text:

The type ‘TimeUpDown’ was not found because ‘clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Input.Toolkit’ is an unknown namespace

This time the fix is to add a reference to "System.Windows.Controls.Input.Toolkit" to the project.

The funny thing is that this project (that uses a library that hosts a control that uses TimeUpDown itself) DOESN’T NEED to have a reference to "System.Windows.Controls", as the library does need to compile.

The other funny thing is that it does compile OK without adding the "System.Windows.Controls.Input.Toolkit" reference, but it shows runtime error.


This issue has been reported for some time now at:


but hasn’t yet been fixed.


This may also be related:


I noticed that when I tried to compile on a machine that didn’t have Silverlight 5 Toolkit, it was eventually trying to use the Silverlight 4 Toolkit version of System.Windows.Control.Input from my Debug folder (not sure how that DLL ended up there, probably was brought in automatically via some other library’s dependencies by Visual Studio). So maybe you end up with multiple assemblies with the same name in the project and you have to remove the old ones.

You may also run into this issue if your solution was using Silverlight 5 Toolkit and you try to build the project on another machine that has Silverlight 4 Toolkit only. Solution is to install Silverlight 5 Toolkit too and then make sure the project refers to the 5.0 version of System.Windows.Controls.Input.Toolkit.dll and that the reference doesn’t have a path that points into your solution but to the program files folder instead, where Silverlight Toolkit gets installed.

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