为什么LINQ to SQL将重复项插入到我的表中？

I have a web service that retrieves reviews from my database and if not enough reviews are returned, it goes to a secondary source and gets them there and caches them in my database. I have recently noticed that it has been creating duplicates in my database despite me having primary keys to prevent it. I was thinking that maybe when I made the table I did something wrong? Here is the SQL create table snippet:I have a web service that retrieves reviews fro