LINQ NullReferenceException was unhandled

Public Class Form1
    Dim db As CEEDataContext
    Private Sub nptItem1A_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles nptItem1E.CheckedChanged, nptItem1D.CheckedChanged, nptItem1C.CheckedChanged, nptItem1B.CheckedChanged, nptItem1A.CheckedChanged
        Dim sItem1 As String = " "
        If nptItem1A.Checked = True Then
            sItem1 = "A"
        ElseIf nptItem1B.Checked = True Then
            sItem1 = "B"
        ElseIf nptItem1C.Checked = True Then
            sItem1 = "C"
        ElseIf nptItem1D.Checked = True Then
            sItem1 = "D"
        ElseIf nptItem1E.Checked = True Then
            sItem1 = "E"
        End If

        'mdiSLUCEE_CBT.CheckConnection()
        giAppNo = 0
        giAppNo = 2084567
        Dim SearchAppNo = From encodedApp In db.tblCEE_Answers _
                          Where encodedApp.AppNo = giAppNo


        If SearchAppNo.Count > 0 Then
            SearchAppNo.First.AppNo = giAppNo
            SearchAppNo.First.NumItem1 = sItem1
            SearchAppNo.First.LastName = gsLastName
            SearchAppNo.First.FirstName = gsFirstName
            SearchAppNo.First.MiddleName = gsMiddleName
            db.SubmitChanges()
        Else
            Dim newRecord As New tblCEE_Answer With _
            {.AppNo = giAppNo, _
             .LastName = gsLastName, _
             .FirstName = gsFirstName, _
             .MiddleName = gsMiddleName, _
             .NumItem1 = sItem1}

            db.tblCEE_Answers.InsertOnSubmit(newRecord)
            db.SubmitChanges()
        End If

    End Sub
End Class
        

I'm getting error in this line

Dim SearchAppNo = From encodedApp In db.tblCEE_Answers _
                          Where encodedApp.AppNo = giAppNo