microsoft.practices.unity Error

I am getting the below error while reading the microsoft.practices.unity configuration section from my project app.config file.

"An error occurred creating the configuration section handler for unity: Value cannot be null."

Also below are the line of codes from my test project which is throwing the above error:

Dim uc = CType(ConfigurationManager.GetSection("unity"), UnityConfigurationSection)

uc.Containers.Default.Configure(u)

Please help me on this..!! Or any reference to the reason for this cause.