I have to insert randomly selected records in database, it can be either update of records or insertion then what is the best way to insert / update mass records?

I have 1 web application in c# & I have to save records in sql server database.
Now it can be insert or update if the same record is already inserted.
I have implemented it using foreach loop but I feel some better method should be available to insert multiple records.

Kindly give some suggestion for the same