Hello ocsjack：)

As far as I see，I think you'd better check a primary key whether it exists in the DataContext first，and then do inserting。

【Sample】

using (EntityContext ec = new EntityContext())
{
    var result = ec.SomeModel.Where(m=>m.PrimaryKey.Equals(your record's id to be inserted)).FirstOrDefault();
    if(result==null)
    {
      //Do inserting here……
    }
}