Code Generating Error using DSL and T4

I've created a DSL model using DSL tools in Visual Studio 2008 as follows ,

In my code generating template(T4) , 

I have tried to extract the property name Called ConnectionString as follows,

<#=SSAS.ConnectionString#>

But It's popping an Error like below.

Compiling transformation: Only assignment, call, increment, decrement, and new object expressions can be used as a statement

Is my statement is an Illegal one ? . How can I over come this ? 

Thanks ,