Can you guys help me to solve testing task!

Guys, can someone write me a test-case?

I need to write test-cases on functionality

To implement web-service which will provide SOAP/HTTP interface for UI application.
Web-service should return in response concatenated value of first name + last name found by user id provided in request to the service.

Information about users is stored in database
USERS table with columns:
User_id (number, PK),
First_name (varchar2(50), nullable=true)
Last_name (varchar2(50), nullable=false)

Thank you!

If you want a test case in SQL see tSQLt. If you want test cases in your .NET code, you might want to post in a visual studio forum

Sounds like homework or an interview question.