# .NET and More > Silverlight >  [RESOLVED] debug silverlight

## arkiboys

Hi,
I am using .net 4 visual studio 2010 premium.
I have been given a silverlight project to work on which was created in silverlight 3.
I can run the application but can not debug it.
The properties of the application shows that the target silverlight version is set to silverlight 3 and this is the only option available.
Note that I have installed silverlight 4.
And in the web.config of the host, the following line is indeed present
<compilation debug="true">

Question:
How can I debug the application based on the above please?
Thanks

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## gep13

Hey,

Have you installed the Developer Runtime of Silverlight 4?  You will need to do this, or Visual Studio will not know how to debug the application.

Gary

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## arkiboys

Thank you

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