Cannot Add An Entity That Already Exists.

 Hello,
         Why do I receive this error "Cannot add an entity that already exists."

         I'm trying to add three data at one call using LINQ, after getting the error above then refreshing the page, only one data is inserted.


...
    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim db As personalDataContext = New personalDataContext
        Dim p As New personal

        For i = 0 To 3 - 1
            p.name = "Mick"
            p.number = "01213"
            p.picture = "image/image.jpg"
            db.personals.InsertOnSubmit(p)
            db.SubmitChanges()
        Next

    End Sub
... 
 
cheers,
imperialx