C# – SQL query or C# .net code for csv files import

My aim here is to find out the best possible and feasible solution for my dilemma. I want to import some csv file (may contain around 50~60K records) into database after some manipulation into the files, manipulation includes comparison such as one record already exists into database or not. I already have a .net c# application which

• gets the file
• fetches its data into datatable
• loop through each record, do comparison for each of the record from database
• and finally updates/creates/deletes record.

this whole process is apparently too time consuming. My client needs this process working as fast as possible. I suggested him to do this import process with SQL only(though I'm not sure whether it would work more efficiently using SQL features such as staging table, temp table and cursors).

Now by SQL this is what I thought could be done in order to get it working better:

• create a staging table
• using BULK IMPORT or SQLBULKCOPY function import all csv file's data into this staging table.
• create a SP which would loop through(using CURSOR ofcourse) all records from staging table and will compare each records from already existing db table and will create/update/delete record accordingly.
• empty staging table.

I'm not sure the SQL version would work more efficiently in my case or not. In total I'm not able to see a clear vision that whether I should go with the SQL version of solution or stick with the current .net C# code and optimize this current code only. It would be great if someone can advise me on the same.

let me explain this with the help of an example:

1. these are the headers of csv file:
   StudentId, StudentFname, StudentLname, ClassName, teacherId, teacherFname, teacherLname
2. suppose I've copied all its data as it is into staging table.
3. now I've to update those students which are already in STUDENT table and create those which do not exist, check if the classname already exists in CLASS table (if not then create class), check if the teacher id already exists in TEACHER table (if not then create teacher, otherwise update it).