เราจะเช็คค่าว่างใน DataTable ได้อย่างไรครับ แนะนำด้วยครับ

Private Sub LoadSizeData()

        If IsNothing(Session("SizeTable")) Then
            dt = New DataTable()
            dt.Columns.Add(New DataColumn("TopWidth", GetType(String)))
            dt.Columns.Add(New DataColumn("MidWidth", GetType(String)))
            dt.Columns.Add(New DataColumn("BottomWidth", GetType(String)))
            dt.Columns.Add(New DataColumn("WidthAVG", GetType(String)))
            dt.Columns.Add(New DataColumn("LeftLength", GetType(String)))
            dt.Columns.Add(New DataColumn("RigthLength", GetType(String)))
            dt.Columns.Add(New DataColumn("LengthAVG", GetType(String)))
            dt.Columns.Add(New DataColumn("SizeNote", GetType(String)))
            Session("SizeTable") = dt
        End If

        dt = DirectCast(Session("SizeTable"), DataTable)
        gvS_LoadSize.DataSource = dt
        gvS_LoadSize.DataBind()

    End Sub

Private Sub AddToTable()

        If txtPK_WidthTop.Text.Trim <> String.Empty And txtPK_WidthMid.Text.Trim <> String.Empty And txtPK_WidthBottom.Text.Trim <> String.Empty And txtPK_LengthLeft.Text.Trim <> String.Empty And txtPK_LengthRigth.Text.Trim <> String.Empty Then

            Dim dr As DataRow = dt.NewRow

            dr("TopWidth") = txtPK_WidthTop.Text.Trim
            dr("MidWidth") = txtPK_WidthMid.Text.Trim
            dr("BottomWidth") = txtPK_WidthBottom.Text.Trim
            'dr("WidthAVG") = ((CType(txtPK_WidthTop.Text.Trim, Integer) + CType(txtPK_WidthMid.Text.Trim, Integer) + CType(txtPK_WidthBottom.Text.Trim, Integer)) / 3).ToString("#,##0.00") 
            'dr("WidthAVG") = ((CType(txtPK_WidthTop.Text.Trim, Integer) + CType(txtPK_WidthMid.Text.Trim, Integer) + CType(txtPK_WidthBottom.Text.Trim, Integer)) / 3).ToString("#0.00") 
            dr("WidthAVG") = ((CType(txtPK_WidthTop.Text.Trim, Decimal) + CType(txtPK_WidthMid.Text.Trim, Decimal) + CType(txtPK_WidthBottom.Text.Trim, Decimal)) / 3).ToString("n2")
            dr("LeftLength") = txtPK_LengthLeft.Text.Trim
            dr("RigthLength") = txtPK_LengthRigth.Text.Trim
            'dr("LengthAVG") = ((CType(txtPK_LengthLeft.Text.Trim, Integer) + CType(txtPK_LengthRigth.Text.Trim, Integer)) / 2).ToString("#,##0.00") 
            'dr("LengthAVG") = ((CType(txtPK_LengthLeft.Text.Trim, Integer) + CType(txtPK_LengthRigth.Text.Trim, Integer)) / 2).ToString("#0.00") 
            dr("LengthAVG") = ((CType(txtPK_LengthLeft.Text.Trim, Decimal) + CType(txtPK_LengthRigth.Text.Trim, Decimal)) / 2).ToString("n2")
            dr("SizeNote") = txtPK_SizeNote.Text.Trim

            dt.Rows.Add(dr)
            Session("SizeTable") = dt
            LoadSizeData()
            Reset()
            txtPK_WidthTop.Focus()

        ElseIf txtPK_WidthTop.Text.Trim = String.Empty And txtPK_WidthMid.Text.Trim <> String.Empty And txtPK_WidthBottom.Text.Trim <> String.Empty And txtPK_LengthLeft.Text.Trim <> String.Empty And txtPK_LengthRigth.Text.Trim <> String.Empty Then
            MsgBox("กรุณากรอกความกว้างส่วนบน")
            txtPK_WidthTop.Focus()
        ElseIf txtPK_WidthTop.Text.Trim <> String.Empty And txtPK_WidthMid.Text.Trim = String.Empty And txtPK_WidthBottom.Text.Trim <> String.Empty And txtPK_LengthLeft.Text.Trim <> String.Empty And txtPK_LengthRigth.Text.Trim <> String.Empty Then
            MsgBox("กรุณากรอกความกว้างส่วนกลาง")
            txtPK_WidthMid.Focus()
        ElseIf txtPK_WidthTop.Text.Trim <> String.Empty And txtPK_WidthMid.Text.Trim <> String.Empty And txtPK_WidthBottom.Text.Trim = String.Empty And txtPK_LengthLeft.Text.Trim <> String.Empty And txtPK_LengthRigth.Text.Trim <> String.Empty Then
            MsgBox("กรุณากรอกความกว้างส่วนล่าง")
            txtPK_WidthBottom.Focus()
        ElseIf txtPK_WidthTop.Text.Trim <> String.Empty And txtPK_WidthMid.Text.Trim <> String.Empty And txtPK_WidthBottom.Text.Trim <> String.Empty And txtPK_LengthLeft.Text.Trim = String.Empty And txtPK_LengthRigth.Text.Trim <> String.Empty Then
            MsgBox("กรุณากรอกความยาวด้านซ้าย")
            txtPK_LengthLeft.Focus()
        ElseIf txtPK_WidthTop.Text.Trim <> String.Empty And txtPK_WidthMid.Text.Trim <> String.Empty And txtPK_WidthBottom.Text.Trim <> String.Empty And txtPK_LengthLeft.Text.Trim <> String.Empty And txtPK_LengthRigth.Text.Trim = String.Empty Then
            MsgBox("กรุณากรอกความยาวด้านขวา")
            txtPK_LengthRigth.Focus()
        Else
            MsgBox("กรุณากรอกข้อมูลให้ครบถ้วน")
            txtPK_WidthTop.Focus()
        End If

    End Sub

    Protected Sub btnPK_Add_Click(sender As Object, e As EventArgs) Handles btnPK_Add.Click

        AddToTable()

    End Sub

Private Sub AddTODB()

        Try
            ConnectDB()
            objConn.Open()

            strSQL = "SELECT ISNULL(MAX(RIGHT(PK_ID,2)),0) As PK_ID FROM Package"
            objCmd = New SqlCommand(strSQL, objConn)

            Count = objCmd.ExecuteScalar()

            iMAX = IIf(Count <= 0, 1, Count + 1)
            If iMAX < 100 Then
                strSQL = "INSERT INTO Package (PK_ID, PK_RECEIVEDATE) VALUES ('" & "PK" & CStr(Format(Now.Date.ToString("yyyyMMdd", New CultureInfo("en-US")))) & iMAX.ToString("00") & "',@PK_RECEIVEDATE)"
                objCmd = New SqlCommand(strSQL, objConn)

                objCmd.Parameters.Add("@PK_RECEIVEDATE", SqlDbType.Date).Value = Format(Now.Date.ToString("dd-MM-yyyy", New CultureInfo("en-US")))
                objCmd.ExecuteNonQuery()

                iMAX = IIf(Count <= 0, 1, Count + 1)
                If iMAX < 100 Then

                    dt = DirectCast(Session("SizeTable"), DataTable)
                    For i = 0 To dt.Rows.Count - 1

                        strSQL = "INSERT INTO Size (PK_ID,S_WIDTHTOP,S_WIDTHMID,S_WIDTHBOTTOM,S_LENGTHLEFT,S_LENGTHRIGTH,S_NOTE) VALUES ('" & "PK" & CStr(Format(Now.Date.ToString("yyyyMMdd", New CultureInfo("en-US")))) & iMAX.ToString("00") & "','" & dt.Rows(i)("TopWidth") & "','" & dt.Rows(i)("MidWidth") & "','" & dt.Rows(i)("BottomWidth") & "','" & dt.Rows(i)("LeftLength") & "','" & dt.Rows(i)("RigthLength") & "','" & dt.Rows(i)("SizeNote") & "')"
                        objCmd = New SqlCommand(strSQL, objConn)


                        With objCmd
                            .Connection = objConn
                            .CommandText = strSQL
                            .CommandType = CommandType.Text
                            .ExecuteNonQuery()
                        End With
                    Next

                    objConn.Close()
                    objConn = Nothing
                    MsgBox("บันทึกข้อมูลสำเร็จ")
                    dt.Clear()
                    Response.Redirect("~/Test/Test_Manage_Package.aspx")

                End If
            Else
                MsgBox("ข้อมูลเต็ม")
            End If

        Catch ex As Exception

            Response.Write("Error : " + ex.Message)

        End Try

    End Sub

    Protected Sub btnPK_Save_Click(sender As Object, e As EventArgs) Handles btnPK_Save.Click

        AddTODB()

    End Sub