เวลาผมกดปุ่ม Cancel เพื่อที่จะเคลียค่าใน DataTable มันต้องกดถึง 2 ครั้งเลยครับ

Imports System.Data.SqlClient
Imports System.Globalization

Public Class Manage_Package
    Inherits System.Web.UI.Page

    Dim objConn As SqlConnection
    Dim objCmd As SqlCommand
    Dim strConnString, strSQL As String
    Dim dtAdapter As SqlDataAdapter
    Dim ds As DataSet
    Dim dt As DataTable
    Dim result, num, iMAX, Count As Integer
    Dim TopWidth As Decimal

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        lblPK_AddReceiveDate.Text = Format(Now.Date.ToString("dd/MM/yyyy", New CultureInfo("en-US")))

        If IsPostBack Then
            LoadSizeData()
        End If

    End Sub

    Public Sub ConnectDB()

        strConnString = ConfigurationManager.ConnectionStrings("con").ConnectionString
        objConn = New SqlConnection(strConnString)

    End Sub

    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, 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, 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()

        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()
            Else
                MsgBox("ข้อมูลเต็ม")
            End If

            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
            Else
                MsgBox("ข้อมูลเต็ม")
            End If

            objConn.Close()
            objConn = Nothing
            MsgBox("บันทึกข้อมูลสำเร็จ")

        Catch ex As Exception

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

        End Try

    End Sub

    Private Sub Reset()

        txtPK_WidthTop.Text = String.Empty
        txtPK_WidthMid.Text = String.Empty
        txtPK_WidthBottom.Text = String.Empty
        txtPK_LengthLeft.Text = String.Empty
        txtPK_LengthRigth.Text = String.Empty

    End Sub

    Private Sub ResetAll()

        Reset()
        dt.Clear()

    End Sub

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

        AddTODB()

    End Sub

    Protected Sub btnPK_Cancel_Click(sender As Object, e As EventArgs) Handles btnPK_Cancel.Click

        ResetAll()

    End Sub

End Class