If you want to save the value into primary column then you just need to do the setting into SQL server.
1. Right click on table name.
2. Select the column name
3. Go into property window
4. Double click on identity specification.
5. Save the table
Now when you run any insert query you dont need to provide this column value it will automatically incremented.
If you want custom sequence number from C# application then you need to execute select query to fetch the last inserted record id with scope_Identity() and need to increment the value.
refer the below link.