How to use Project Level connection Managers in SSIS Script Task

Question

I've a Project level connection managers which are used across multiple packages when I'm trying to use the same connection manager in SSIS Script tasks like below but getting null value in myADONETConnection

SqlConnection myADONETConnection = new SqlConnection();
            myADONETConnection =
            Dts.Connections["projectconnectionmanager"].AcquireConnection(Dts.Transaction) as SqlConnection;

but when use the package level conenction manager in same way myADONETConnection is getting values

SqlConnection myADONETConnection = new SqlConnection();
                myADONETConnection =
                Dts.Connections["packageconnectionmanager"].AcquireConnection(Dts.Transaction) as SqlConnection;

not sure what should be changed for project level connection manager could someone please help me on this