Key Dependency problem.

Hi All,
I have to develop the Key dependecy cache techniques. I have tried this. i got the error. I have shown the details below.
 
HttpContext.Current.Cache.Insert(
Dim MyDependency As New CacheDependency(Nothing, keys)"SqlPubsEmployees", ds, MyDependency)
 
 
When i run this code, its throughing the error.Please give me some code to implement the Key Dependency.
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