Crm 2011 : The type or namespace name 'Metadata' does not exist in the namespace 'Microsoft.Xrm.Client' (are you missing an assembly reference?)

Hi,

i am creating a library project that connects to crm. i am using the example in the following msdn article

http://msdn.microsoft.com/en-us/library/gg695790.aspx

i used this process a number of times to connect a third party website to crm. this is the first time i am doing it in library project. but every time i build the project i come up with the error mentioned in the subject. 

my project is already set up in .net 4.0. any idea on the error will be hugely appreciated. 

regards

im