NullRefference exception when calling a .net method

 I am trying to call a .net method from Biztalk 2010 orchestration. I used the following code..getStudentInfo() method takes a string 'studentId' as parameter and returns a populated object 'student'. Created student as variable of .net type 'StudClassLibrary.Student'  (I am able to call the same method with out any issue from a console application and it returns the value.)

Student = new StudClassLibrary.Student();
Student = Student.getStudentInfo(StudentInputMsg.StudentId);

I get the following exception: Appreciate any help! Thanks!!!

unexpected exception.
InstanceId: d1120e02-5d84-474b-847a-f87c24354bd2
Shape name: Expr_GetStudentInfo
ShapeId: b60b169d-67db-479e-adc1-fef1680f9e83
Exception thrown from: segment 1, progress 13
Inner exception: Object reference not set to an instance of an object.
       
Exception type: NullReferenceException
Source: StudClassLibrary
Target Site: StudClassLibrary.Student getStudentInfo(System.String)
The following is a stack trace that identifies the location where the exception occured

   at StudClassLibrary.Student.getStudentInfo(String studId)
   at TestBiztalkApplication.GetStudentInfo.segment1(StopConditions stopOn)
   at Microsoft.XLANGs