If you concatenate string values in C#, you can use + The same applies to SQL Server if you concatenate varchar values in an SQL statement
Addition, example of concatenating in SQL
If you want to concatenate twu strings in the SQL statement, lets say col1 and col2 (both varchar) then your statement could look something like:
SELECT Col1 + Col2, ... other columns ...
FROM TIMETABLE
WHERE DEPARTMENT_CODE = @depcodeparameter
AND TIME = @sometimeparameter
AND SEMESTER = @semesterparame