เพิ่มข้อมูลใน DataTable แล้วข้อมูลใหม่ทับข้อมูลเก่า (เทพ ASP.NET ช่วยหน่อยนะค่ะ แก้มาสามวันแล้ว)

Dim dt As New DataTable()
Dim ds As New DataSet
Dim dr As DataRow

Public Function newDataTable()
        Dim dt As New DataTable()
        Dim ds As New DataSet
        Dim dr As DataRow

        dt.Columns.Add(New DataColumn("NO.", GetType(Integer)))
        dt.Columns("NO.").AutoIncrement = True
        dt.Columns("NO.").AutoIncrementSeed = 1

        dt.Columns.Add(New DataColumn("ชื่ออาหาร", GetType(String)))
        dt.Columns.Add(New DataColumn("ร้านอาหาร", GetType(String)))
        dt.Columns.Add(New DataColumn("เพิ่มเติม", GetType(String)))
        dt.Columns.Add(New DataColumn("จำนวน/หน่วย", GetType(Integer)))
        dt.Columns.Add(New DataColumn("ราคา", GetType(Integer)))
        dt.Columns.Add(New DataColumn("ราคารวม", GetType(Integer)))

        dr = dt.NewRow()
        dr("ชื่ออาหาร") = ddlmenu.SelectedItem.Text.Trim
        dr("ร้านอาหาร") = ddlstore2.SelectedItem.Text.Trim

        'For i = 0 To cboxOption.Items.Count - 1
        '    If cboxOption.Items(i).Selected Then
        '        Dim chk As String
        '        chk = cboxOption.SelectedItem.Text & "," & cboxOption.Items(i).Text
        '        'cboxOption.SelectedItem.Text = cboxOption.SelectedItem.Text & "," & cboxOption.Items(i).Text
        '        dr("เพิ่มเติม") = chk
        '    End If
        'Next

        Dim check As String = ""
        For Each li As ListItem In cboxOption.Items
            If li.Selected Then
                If check = "" Then
                    check = (li.Text)
                    dr("เพิ่มเติม") = check
                Else
                    check += ("," + li.Text)
                    dr("เพิ่มเติม") = check
                End If
            End If
        Next

        dr("จำนวน/หน่วย") = txtquantity.Text.Trim
        dr("ราคา") = txtunitPrice.Text.Trim
        dr("ราคารวม") = (txtquantity.Text) * (txtunitPrice.Text)
        dt.Rows.Add(dr)

        ds.Tables.Add(dt)
        GridView1.DataSource = dt
        GridView1.DataBind()

        Return dt
    End Function

Protected Sub btnadd_Click(sender As Object, e As ImageClickEventArgs) Handles btnadd.Click
        newDataTable()
    End Sub

Public Class WebForm1
    Inherits System.Web.UI.Page
        Dim dt As New DataTable()
        Dim ds As New DataSet
        Dim dr As DataRow
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        dt.Columns.Add(New DataColumn("NO.", GetType(Integer)))
        dt.Columns("NO.").AutoIncrement = True
        dt.Columns("NO.").AutoIncrementSeed = 1

        dt.Columns.Add(New DataColumn("ชื่ออาหาร", GetType(String)))
        dt.Columns.Add(New DataColumn("ร้านอาหาร", GetType(String)))
        dt.Columns.Add(New DataColumn("เพิ่มเติม", GetType(String)))
        dt.Columns.Add(New DataColumn("จำนวน/หน่วย", GetType(Integer)))
        dt.Columns.Add(New DataColumn("ราคา", GetType(Integer)))
        dt.Columns.Add(New DataColumn("ราคารวม", GetType(Integer)))
    End Sub

    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    End Sub

Public Function newDataTable()



        dr = dt.NewRow()
        dr("ชื่ออาหาร") = ddlmenu.SelectedItem.Text.Trim
        dr("ร้านอาหาร") = ddlstore2.SelectedItem.Text.Trim

        'For i = 0 To cboxOption.Items.Count - 1
        '    If cboxOption.Items(i).Selected Then
        '        Dim chk As String
        '        chk = cboxOption.SelectedItem.Text & "," & cboxOption.Items(i).Text
        '        'cboxOption.SelectedItem.Text = cboxOption.SelectedItem.Text & "," & cboxOption.Items(i).Text
        '        dr("เพิ่มเติม") = chk
        '    End If
        'Next

        Dim check As String = ""
        For Each li As ListItem In cboxOption.Items
            If li.Selected Then
                If check = "" Then
                    check = (li.Text)
                    dr("เพิ่มเติม") = check
                Else
                    check += ("," + li.Text)
                    dr("เพิ่มเติม") = check
                End If
            End If
        Next

        dr("จำนวน/หน่วย") = txtquantity.Text.Trim
        dr("ราคา") = txtunitPrice.Text.Trim
        dr("ราคารวม") = (txtquantity.Text) * (txtunitPrice.Text)
        dt.Rows.Add(dr)

        ds.Tables.Add(dt)
        GridView1.DataSource = dt
        GridView1.DataBind()

        Return dt
    End Function
End Class

    Dim dt As New DataTable()
    Dim ds As New DataSet
    Dim dr As DataRow

    Dim con As String = ConfigurationManager.ConnectionStrings("con").ConnectionString
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If Not IsPostBack Then
            CheckBoxListDataTable()
            'txtfoodDetails.ReadOnly = True
            loadddlstore()
        End If

        dt.Columns.Add(New DataColumn("NO.", GetType(Integer)))
        dt.Columns("NO.").AutoIncrement = True
        dt.Columns("NO.").AutoIncrementSeed = 1

        dt.Columns.Add(New DataColumn("ชื่ออาหาร", GetType(String)))
        dt.Columns.Add(New DataColumn("ร้านอาหาร", GetType(String)))
        dt.Columns.Add(New DataColumn("เพิ่มเติม", GetType(String)))
        dt.Columns.Add(New DataColumn("จำนวน", GetType(Integer)))
        dt.Columns.Add(New DataColumn("ราคา/หน่วย", GetType(Decimal)))
        dt.Columns.Add(New DataColumn("ราคารวม", GetType(Decimal)))

        '**** DateToday ***'
        txtdate.Text = Date.Today()
    End Sub

    Sub CheckBoxListDataTable()
        Dim SqlCon As New SqlConnection(con)
        Dim da As New SqlDataAdapter
        Dim dt As New DataTable

        SqlCon.Open()
        Dim strSQL As String
        strSQL = "SELECT * FROM OptionFood"
        da = New SqlDataAdapter(strSQL, SqlCon)
        da.Fill(dt)

        da = Nothing
        SqlCon.Close()
        SqlCon = Nothing

        With cboxOption
            .DataSource = dt
            .DataTextField = "OptionName"
            .DataValueField = "rkey"
            .DataBind()
        End With

        'cboxOption.SelectedIndex = cboxOption.Items.IndexOf(cboxOption.Items.FindByValue("1"))
    End Sub

    Protected Sub loadddlstore()
        ddlstore2.AppendDataBoundItems = True
        Dim sqlCon As New SqlConnection(con)
        Dim da As New SqlDataAdapter
        Dim dt As New DataTable

        sqlCon.Open()
        Dim strSQL As String
        strSQL = "SELECT storeID, storeName FROM Store WHERE online = '1'"
        da = New SqlDataAdapter(strSQL, sqlCon)
        da.Fill(dt)

        da = Nothing
        sqlCon.Close()
        sqlCon = Nothing

        Try
            With ddlstore2
                .DataSource = dt
                .DataTextField = "storeName"
                .DataValueField = "storeID"
                .DataBind()
                .Items.Insert(0, New ListItem("กรุณาเลือกร้านอาหาร", "0"))
            End With

            ddlstore2.SelectedIndex = ddlstore2.Items.IndexOf(ddlstore2.Items.FindByValue("0"))
        Catch ex As Exception
            Throw ex
        End Try
    End Sub

    Protected Sub ddlstore2_SelectIndexChanged(sender As Object, e As EventArgs)
        ddlstore2.AppendDataBoundItems = True
        Dim sqlCon As New SqlConnection(con)
        Dim strSQL As String
        Dim cmd As New SqlCommand()

        strSQL = "SELECT rkey,foodName FROM StoreFood WHERE statusonline='1' AND storeID=@storeID"
        cmd.Parameters.AddWithValue("@storeID", ddlstore2.SelectedItem.Value)
        cmd.CommandType = CommandType.Text
        cmd.CommandText = strSQL
        cmd.Connection = sqlCon
        Try
            sqlCon.Open()
            ddlmenu.DataSource = cmd.ExecuteReader()
            ddlmenu.DataTextField = "foodName"
            ddlmenu.DataValueField = "rkey"
            ddlmenu.DataBind()
            ddlmenu.Items.Insert(0, New ListItem("กรุณาเลือกรายการอาหาร", "0"))

            ddlmenu.SelectedIndex = ddlmenu.Items.IndexOf(ddlmenu.Items.FindByValue("0"))

            If ddlmenu.Items.Count > 1 Then
                ddlmenu.Enabled = True
            Else
                ddlmenu.Enabled = False
            End If
        Catch ex As Exception
            Throw ex
        Finally
            sqlCon.Close()
            sqlCon.Dispose()
        End Try

    End Sub

    Protected Sub ddlmenu_SelectIndexChanged(sender As Object, e As EventArgs)
        Dim sqlCon As New SqlConnection(con)
        Dim strSQL As String
        Dim cmd As New SqlCommand()

        strSQL = "SELECT foodDetails,foodPic,unitPrice FROM StoreFood WHERE rkey=@rkey"
        cmd.Parameters.AddWithValue("@rkey", ddlmenu.SelectedItem.Value)
        cmd.CommandType = CommandType.Text
        cmd.CommandText = strSQL
        cmd.Connection = sqlCon
        Try
            sqlCon.Open()
            Dim sdr As SqlDataReader = cmd.ExecuteReader()
            While sdr.Read()
                Imagefood.Visible = True
                Label3.Visible = True
                Label3.Text = sdr("foodDetails").ToString()
                txtunitPrice.Text = sdr("unitPrice").ToString()
                'txtfoodDetails.Visible = True
                'txtfoodDetails.Text = sdr(0).ToString()
                Imagefood.ImageUrl = sdr("foodPic").ToString()
            End While
        Catch ex As Exception
            Throw ex
        Finally
            sqlCon.Close()
            sqlCon.Dispose()
        End Try
    End Sub


    Protected Sub btnadd_Click(sender As Object, e As ImageClickEventArgs) Handles btnadd.Click
        newDataTable()
        ResetAll()
    End Sub

    Public Function newDataTable()
        If dt.Columns.Count = 0 Then
            dt.Columns.Add("ชื่ออาหาร")
            dt.Columns.Add("ร้านอาหาร")
            dt.Columns.Add("เพิ่มเติม")
            dt.Columns.Add("จำนวน")
            dt.Columns.Add("ราคา/หน่วย")
            dt.Columns.Add("ราคารวม")
        End If

        dr = dt.NewRow()

        dr("ชื่ออาหาร") = ddlmenu.SelectedItem.Text.Trim
        dr("ร้านอาหาร") = ddlstore2.SelectedItem.Text.Trim

        'For i = 0 To cboxOption.Items.Count - 1
        '    If cboxOption.Items(i).Selected Then
        '        Dim chk As String
        '        chk = cboxOption.SelectedItem.Text & "," & cboxOption.Items(i).Text
        '        'cboxOption.SelectedItem.Text = cboxOption.SelectedItem.Text & "," & cboxOption.Items(i).Text
        '        dr("เพิ่มเติม") = chk
        '    End If
        'Next

        Dim check As String = ""
        For Each li As ListItem In cboxOption.Items
            If li.Selected Then
                If check = "" Then
                    check = (li.Text)
                    dr("เพิ่มเติม") = check
                Else
                    check += ("," + li.Text)
                    dr("เพิ่มเติม") = check
                End If
            End If
        Next

        dr("จำนวน") = Integer.Parse(txtquantity.Text.Trim)
        dr("ราคา/หน่วย") = Decimal.Parse(txtunitPrice.Text.Trim)

        Dim amount As String = Decimal.Parse((txtquantity.Text) * (txtunitPrice.Text))
        dr("ราคารวม") = FormatNumber(amount, 2)
        dt.Rows.Add(dr)

        ds.Tables.Add(dt)
        GridView1.DataSource = dt
        GridView1.DataBind()

        Return dt
    End Function

    Protected Sub ResetAll()
            ddlstore2.SelectedIndex = ddlmenu.Items.IndexOf(ddlmenu.Items.FindByValue("0"))
            ddlmenu.SelectedIndex = ddlmenu.Items.IndexOf(ddlmenu.Items.FindByValue("0"))
            cboxOption.SelectedIndex = cboxOption.Items.IndexOf(cboxOption.Items.FindByValue("0"))
            txtquantity.Text = String.Empty
            txtunitPrice.Text = String.Empty
        End Sub
    End Class

Public Function newDataTable()
    If dt.Columns.Count = 0 Then
        dt.Columns.Add("ชื่ออาหาร")
        dt.Columns.Add("ร้านอาหาร")
        dt.Columns.Add("เพิ่มเติม")
        dt.Columns.Add("จำนวน")
        dt.Columns.Add("ราคา/หน่วย")
        dt.Columns.Add("ราคารวม")
    End If

    Dim check As String = ""
    For Each li As ListItem In cboxOption.Items
        If li.Selected Then
            If check = "" Then
                check = (li.Text)
            Else
                check += ("," + li.Text)
            End If
        End If
    Next

    Dim amount As String = Decimal.Parse((txtquantity.Text) * (txtunitPrice.Text))
    Dim dr As DataRow = dt.NewRow()
    dr("ชื่ออาหาร") = ddlmenu.SelectedItem.Text.Trim
    dr("ร้านอาหาร") = ddlstore2.SelectedItem.Text.Trim
    dr("เพิ่มเติม") = check
    dr("จำนวน") = Integer.Parse(txtquantity.Text.Trim)
    dr("ราคา/หน่วย") = Decimal.Parse(txtunitPrice.Text.Trim)
    dr("ราคารวม") = FormatNumber(amount, 2)
    dt.Rows.Add(dr)
    GridView1.DataSource = dt
    GridView1.DataBind()

End Function

Public Function newDataTable()

        ' If dt.Columns.Count = 0 Then
        'dt.Columns.Add("ชื่ออาหาร")
        ' dt.Columns.Add("ร้านอาหาร")
        ' dt.Columns.Add("เพิ่มเติม")
        ' dt.Columns.Add("จำนวน")
        ' dt.Columns.Add("ราคา/หน่วย")
        ' dt.Columns.Add("ราคารวม")
        ' End If

        ' Dim check As String = ""
        ' For Each li As ListItem In cboxOption.Items
        'If li.Selected Then
        'If check = "" Then
        'check = (li.Text)
        'Else
        'check += ("," + li.Text)
        'End If
        'End If
        'Next

        'Dim amount As String = Decimal.Parse((txtquantity.Text) * (txtunitPrice.Text))
        For i As Integer = 0 To 50
            Dim dr As DataRow = dt.NewRow()
            dr("ชื่ออาหาร") = "ชื่ออาหาร " & i
            dr("ร้านอาหาร") = "ร้านอาหาร " & i
            dr("เพิ่มเติม") = "เพิ่มเติม " & i
            dr("จำนวน") = New Random().Next
            dr("ราคา/หน่วย") = New Random().Next
            dr("ราคารวม") = New Random().Next
            dt.Rows.Add(dr)
        Next

        GridView1.DataSource = dt
        GridView1.DataBind()

    End Function

Session("DT") = xxx
'หรือ
ViewState("DT") = xxx

<asp:GridView ID="GridView1" runat="server" DataKeyNames="NO"
                            ShowHeaderWhenEmpty="true" EmptyDataText="ไม่มีสินค้าในตะกร้า" EmptyDataRowStyle-BackColor="#FFFFCC" 
                            EmptyDataRowStyle-ForeColor ="Red" EmptyDataRowStyle-Font-Bold="true"
                            Width="1100px"
                            AutoGenerateColumns="true"
                            HeaderStyle-Font-Bold="true" Style="text-align: center" CellPadding="4" ForeColor="#333333" GridLines="None" ShowFooter="true">
                            <AlternatingRowStyle BackColor="White" />
                               <Columns>
                                   <asp:BoundField DataField="NO" HeaderText="NO." />
                                   <asp:BoundField DataField="foodName" HeaderText="ชื่ออาหาร" />
                                   <asp:BoundField DataField="store" HeaderText="ร้านอาหาร" />
                                   <asp:BoundField DataField="option" HeaderText="สั่งเพิ่มเติม" />
                                   <asp:BoundField DataField="QTY" HeaderText="จำนวน" />
                                   <asp:BoundField DataField="price" HeaderText="ราคา/หน่วย" />
                                   <asp:BoundField DataField="amount" HeaderText="ราคารวม" />
                               </Columns>
                            <FooterStyle BackColor="#FF9933" Font-Bold="True" ForeColor="#363422" />
                            <HeaderStyle Font-Bold="True" BackColor="#FF9933" ForeColor="#363422"></HeaderStyle>
                            <PagerStyle BackColor="#FF9933" ForeColor="#363422" HorizontalAlign="Center"  />
                            <RowStyle BackColor="#FFFFCC" />
                            <SelectedRowStyle BackColor="#FF9933" Font-Bold="True" ForeColor="#333333" />
                            <SortedAscendingCellStyle BackColor="#fff" />
                            <SortedAscendingHeaderStyle BackColor="#fff" />
                            <SortedDescendingCellStyle BackColor="#fff" />
                            <SortedDescendingHeaderStyle BackColor="#fff" />
                        </asp:GridView>

Dim dt As New DataTable
    Dim con As String = ConfigurationManager.ConnectionStrings("con").ConnectionString
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If Not IsPostBack Then
            CheckBoxListDataTable()
            loadddlstore()
        End If

        '**** DATE TODAY ***'
        txtdate.Text = Date.Today()

    End Sub

    Sub CheckBoxListDataTable()
        Dim SqlCon As New SqlConnection(con)
        Dim da As New SqlDataAdapter
        Dim dt As New DataTable

        SqlCon.Open()
        Dim strSQL As String
        strSQL = "SELECT * FROM OptionFood"
        da = New SqlDataAdapter(strSQL, SqlCon)
        da.Fill(dt)

        da = Nothing
        SqlCon.Close()
        SqlCon = Nothing

        With cboxOption
            .DataSource = dt
            .DataTextField = "OptionName"
            .DataValueField = "rkey"
            .DataBind()
        End With

        'cboxOption.SelectedIndex = cboxOption.Items.IndexOf(cboxOption.Items.FindByValue("1"))
    End Sub

    Protected Sub loadddlstore()
        ddlstore2.AppendDataBoundItems = True
        Dim sqlCon As New SqlConnection(con)
        Dim da As New SqlDataAdapter
        Dim dt As New DataTable
        Dim strSQL As String

        sqlCon.Open()
        strSQL = "SELECT storeID, storeName FROM Store WHERE online = '1'"
        da = New SqlDataAdapter(strSQL, sqlCon)
        da.Fill(dt)

        da = Nothing
        sqlCon.Close()
        sqlCon = Nothing

        Try
            With ddlstore2
                .DataSource = dt
                .DataTextField = "storeName"
                .DataValueField = "storeID"
                .DataBind()
                .Items.Insert(0, New ListItem("--- กรุณาเลือกร้านอาหาร ---", "0"))
            End With

            ddlstore2.SelectedIndex = ddlstore2.Items.IndexOf(ddlstore2.Items.FindByValue("0"))
        Catch ex As Exception
            Throw ex
        End Try
    End Sub

    Protected Sub ddlstore2_SelectIndexChanged(sender As Object, e As EventArgs)
        ddlstore2.AppendDataBoundItems = True
        Dim sqlCon As New SqlConnection(con)
        Dim strSQL As String
        Dim cmd As New SqlCommand()

        strSQL = "SELECT rkey,foodName FROM StoreFood WHERE statusonline='1' AND storeID=@storeID"
        cmd.Parameters.AddWithValue("@storeID", ddlstore2.SelectedItem.Value)
        cmd.CommandType = CommandType.Text
        cmd.CommandText = strSQL
        cmd.Connection = sqlCon
        Try
            sqlCon.Open()
            ddlmenu.DataSource = cmd.ExecuteReader()
            ddlmenu.DataTextField = "foodName"
            ddlmenu.DataValueField = "rkey"
            ddlmenu.DataBind()
            ddlmenu.Items.Insert(0, New ListItem("--- กรุณาเลือกรายการอาหาร ---", "0"))

            ddlmenu.SelectedIndex = ddlmenu.Items.IndexOf(ddlmenu.Items.FindByValue("0"))

            If ddlmenu.Items.Count > 1 Then
                ddlmenu.Enabled = True
            Else
                ddlmenu.Enabled = False
            End If
        Catch ex As Exception
            Throw ex
        Finally
            sqlCon.Close()
            sqlCon.Dispose()
        End Try

    End Sub

    Protected Sub ddlmenu_SelectIndexChanged(sender As Object, e As EventArgs)
        Dim sqlCon As New SqlConnection(con)
        Dim strSQL As String
        Dim cmd As New SqlCommand()

        strSQL = "SELECT foodDetails,foodPic FROM StoreFood WHERE rkey=@rkey"
        cmd.Parameters.AddWithValue("@rkey", ddlmenu.SelectedItem.Value)
        cmd.CommandType = CommandType.Text
        cmd.CommandText = strSQL
        cmd.Connection = sqlCon
        Try
            sqlCon.Open()
            Dim sdr As SqlDataReader = cmd.ExecuteReader()
            While sdr.Read()
                If ddlstore2.Items.Count > 1 Then
                    Imagefood.Visible = True
                    txtfoodDetails.Text = sdr(0).ToString()
                    Imagefood.ImageUrl = sdr("foodPic").ToString()
                Else
                    txtfoodDetails.Text = String.Empty
                End If
            End While
        Catch ex As Exception
            Throw ex
        Finally
            sqlCon.Close()
            sqlCon.Dispose()
        End Try
    End Sub

    Protected Sub btnadd_Click(sender As Object, e As ImageClickEventArgs) Handles btnadd.Click
        load_Cart()
    End Sub

    Public Sub Cart()
        If dt.TableName.Contains("tblShopCart") = True Then
            Exit Sub
        Else
            dt = New DataTable("tblShopCaet")
            dt.Columns.Add(New DataColumn("NO", GetType(Integer)))
            dt.Columns("NO").AutoIncrement = True
            dt.Columns("NO").AutoIncrementSeed = 1

            dt.Columns.Add(New DataColumn("foodName", GetType(String)))
            dt.Columns.Add(New DataColumn("store", GetType(String)))
            dt.Columns.Add(New DataColumn("option", GetType(String)))
            dt.Columns.Add(New DataColumn("QTY", GetType(Integer)))
            dt.Columns.Add(New DataColumn("price", GetType(Decimal)))
            dt.Columns.Add(New DataColumn("amount", GetType(Decimal)))
        End If
        Session("ShopCart") = dt
    End Sub

    Public Sub newDataTable()
        Dim check As String = ""
        For Each li As ListItem In cboxOption.Items
            If li.Selected Then
                If check = "" Then
                    check = (li.Text)
                Else
                    check += ("," + li.Text)
                End If
            End If
        Next

        Dim amount As String = Decimal.Parse((txtquantity.Text) * (txtunitPrice.Text))
        Dim dt As DataTable = Session("ShopCart")
        If dt.Rows.Count <= 0 Then
            Dim dr As DataRow = dt.NewRow()
            dr("foodName") = ddlmenu.SelectedItem.Text.Trim
            dr("store") = ddlstore2.SelectedItem.Text.Trim
            dr("option") = check
            dr("QTY") = Integer.Parse(txtquantity.Text.Trim)
            dr("price") = Decimal.Parse(txtunitPrice.Text.Trim)
            dr("amount") = FormatNumber(amount, 2)
            dt.Rows.Add(dr)
            Session("ShopCart") = dt
            Exit Sub
        End If

    End Sub

    Public Sub load_Cart()
        If Session("ShopCart") Is Nothing Then
            GridView1.DataSource = ""
            GridView1.DataBind()
        Else
            GridView1.DataSource = Session("ShopCart")
            GridView1.DataBind()
        End If
    End Sub

End Class