static void Main(string[] args) { using (var db = new DbManager()) { db.SetSpCommand(""); // ok db.SetInsertCommand(""); // ok db.SetUpdateCommand(""); // ok db.Prepare(); // ok db.ExecuteNonQuery(); // ok db.SetCommand(""); // ERROR: // error CS0584: Internal compiler error: Object reference not set to an instance of an object // error CS0201: Only assignment, call, increment, decrement, and new object expressions can be used as a statement } }