Can't run the demo - please help...

May 19, 2009 at 10:31 AM

Hi, I'm new to Silverlight so please forgive this stupid question.  I downloaded the "Full Source Code and Demo" file from the Downloads page.  I opened the "SL_Drag_Drop.sln" file using Visual Web Designer 2008 Express.  When I try to build and run the solution, I get the error below.  Could someone please tell me what I'm doing wrong?

Thanks a lot in advance,




Server Error in '/' Application.

Parser Error

Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

Parser Error Message: Could not load file or assembly 'System.Web.Silverlight' or one of its dependencies. The system cannot find the file specified.

Source Error:

Line 1:  <%@ Page Language="C#" AutoEventWireup="true" %>
Line 2: 
Line 3:  <%@ Register Assembly="System.Web.Silverlight" Namespace="System.Web.UI.SilverlightControls" TagPrefix="asp" %>
Line 4: 
Line 5:  <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

Source File: /SL_Drag_DropTestPage.aspx    Line: 3

Assembly Load Trace: The following information can be helpful to determine why the assembly 'System.Web.Silverlight' could not be loaded.

=== Pre-bind state information ===
LOG: User = WINXP-3CF9F7E20\Administrator
LOG: DisplayName = System.Web.Silverlight
LOG: Appbase = file:///C:/Documents and Settings/Administrator/Desktop/DragDropManager_DemoAndSource/SL_Drag_Drop/SL_Drag_Drop.Web/
LOG: Initial PrivatePath = C:\Documents and Settings\Administrator\Desktop\DragDropManager_DemoAndSource\SL_Drag_Drop\SL_Drag_Drop.Web\bin
Calling assembly : (Unknown).
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Documents and Settings\Administrator\Desktop\DragDropManager_DemoAndSource\SL_Drag_Drop\SL_Drag_Drop.Web\web.config
LOG: Using machine configuration file from C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\config\machine.config.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: The same bind was seen before, and was failed with hr = 0x80070002.

Version Information: Microsoft .NET Framework Version:2.0.50727.3053; ASP.NET Version:2.0.50727.3053

May 19, 2009 at 10:41 AM

Hi there,


this looks as if the base Silverlight assembly(ies) can't be loaded.  Few things to check:

1) is the Silverlight SDK correctly installed on your computer (check this by trying to create a new SL-project and running it)?

2) are the references of the project valid?  Eg: if you have installed the SDK, do the references refer to existing files (they should, if not, you can try manually browsing to the necessary assemblies)

May 19, 2009 at 11:02 AM

KevD, thanks very much for the quick reply.  Yes, I can create a new SL-project and run it.  I'm not quite sure how to check if the references refer to existing files.  When I check under "SL_Drag_Drop.Web" -> "References", there is an exclamation mark by "System.Web.Silverlight".  I presume this is the problem but am not sure how to fix it.

Thanks for your patience,


May 19, 2009 at 11:07 AM

Hi Luck,

if there's an exclamation mark next to that reference, I assume the file is missing from the location where the project expects it to be.  You can solve this by removing that reference, and re-adding a reference to the System.Web.Silverlight-assembly (browse to where that assembly is on your computer).

Hope this helps! :-)


May 19, 2009 at 4:43 PM

KevD, thanks for all of your help.

Much appreciated!