ช่วยดูcode vb.net ให้หน่อยค่ะ error Object reference not set to an instance of an object.

Imports System.Data
Imports System.Data.SqlClient
Imports System.IO

Partial Public Class WebForm17
    Inherits System.Web.UI.Page
    Dim Service As New WebService1
    Dim ConnStr As String = "server=(local);database=police;uid=police;password=police"
    Dim Conn As New SqlConnection(ConnStr)
    Dim strPeID As String = ""
    Dim Sql As String
    'Dim Sql As String = "SELECT * FROM TblPersonel"
    Dim Cmd As SqlCommand
    'Dim Idx As String = Request.QueryString("id")


    Dim MyDa As New SqlDataAdapter(Sql, Conn)
    Dim Da As New SqlDataAdapter
    Dim Ds As New DataSet

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        GridView1.AllowPaging = True
        GridView1.PageSize = 5

        If Not Page.IsPostBack Then
            GridView1.DataSource = CreateDataTable()
            GridView1.DataBind()

            'ReadSIdToDdl()
        End If
    End Sub

    '*** DataTable ***'
    Protected Function CreateDataTable() As DataTable
        Dim strConnString As String = "server=(local);database=police;uid=police;password=police"
        Dim objConn As New SqlConnection(strConnString)

        Dim strCmdString As String = "SELECT * FROM [TblCheckEvent]"
        Dim objCmd As New SqlCommand(strCmdString, objConn)

        Dim Dt As New DataTable()
        Dim objAdapter As New SqlDataAdapter(objCmd)
        objAdapter.Fill(Dt)

        Return Dt '*** Return DataTable ***' 
    End Function

    Sub Search(ByVal SqlSearch As String)
        Dim Found As Boolean = False
        Dim DView As DataView
        'Sql = "Select * From Stock Where SId=" + "'" + Request.Form("TId") + "'" + " Order by SId "
        Da = New SqlDataAdapter(SqlSearch, Conn)
        Da.Fill(Ds, "TblCheckEvent")
        DView = Ds.Tables("TblCheckEvent").DefaultView
        If DView.Count <= 0 Then 'ถ้า DView.Count มีค่ามากกว่า 0 แสดงว่ามีข้อมูลรหัสนั้นๆ แล้ว
            Found = False
            MsgBox("ค้นหาข้อมูลไม่พบ")
            GridView1.Visible = False
            Exit Sub
        Else
            Found = True
            GridView1.Visible = True
            'LMsg.Text = "<Center>...มีข้อมูลรหัส :" & TId.Text & "จ้า...</Center>"
            GridView1.DataSource = Ds.Tables("TblCheckEvent").DefaultView
            'GridView1.DataKeyField = "Pe_Id"
            GridView1.DataBind()
            Conn.Close()
        End If
    End Sub


    Sub SearchField()
        If Len(Trim(TxtSearch.Text)) <= 0 Then
            Response.Write("<script language=javascript>alert('กรุณาใส่ข้อมูลสำหรับการค้นหา');</script")
        Else
            If UCase(DdlField.SelectedItem.Value) = UCase("Date") Then
                'Sql = "Select * From TblPersonel Where Pe_Id ="
                Sql = "Select * From TblCheckEvent Where Ch_DateAccident Like"
                Sql = Sql & "'%" & Trim(TxtSearch.Text) & "%'"
            ElseIf UCase(DdlField.SelectedItem.Value) = UCase("StyleEvents") Then
                Sql = "Select * From TblCheckEvent Where Ch_StyleEvents	 Like"  '//Likeเป็นการค้นหาแบบตัวใดตัวหนึ่งก็ได้แต่ต้องให้%ปิดหัวท้าย
                Sql = Sql & "'%" & Trim(TxtSearch.Text) & "%'"
            Else
                Sql = "Select * From TblCheckEvent Where Ch_CheifInspector	 Like"  '//Likeเป็นการค้นหาแบบตัวใดตัวหนึ่งก็ได้แต่ต้องให้%ปิดหัวท้าย
                Sql = Sql & "'%" & Trim(TxtSearch.Text) & "%'"
                'Else
                '    Sql = "Select * From T Where Zipcode ="
                '    Sql = Sql & "'" & Val(TxtSearch.Text) & "'"
            End If
        End If
        Search(Sql)
    End Sub

    Protected Sub DdlField_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles DdlField.SelectedIndexChanged
        SearchField()
    End Sub

    Protected Sub BtnGo_Click(ByVal sender As Object, ByVal e As EventArgs) Handles BtnGo.Click
        SearchField()
    End Sub





    Protected Sub DetailsViewBindData()

        Sql = "SELECT * FROM TblCheckEvent WHERE Ch_Id = '" & strPeID & "' "
        Dim dtReader As SqlDataReader
        Cmd = New SqlCommand(Sql, Conn)
        Conn.Open()
        dtReader = Cmd.ExecuteReader()

        '*** BindData to DetailsView ***'
        DetailsView1.DataSource = dtReader
        DetailsView1.DataBind()


        dtReader.Close()
        dtReader = Nothing

    End Sub

    Protected Sub Page_Unload(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Unload
        Conn.Close()
        Conn = Nothing
    End Sub



    Private Sub GridView1_PageIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewPageEventArgs) Handles GridView1.PageIndexChanging
        GridView1.DataSource = CreateDataTable()
        GridView1.PageIndex = e.NewPageIndex
        GridView1.DataBind()
    End Sub


    Private Sub GridView1_RowEditing(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewEditEventArgs) Handles GridView1.RowEditing
        GridView1.Visible = False
        strPeID = GridView1.DataKeys(e.NewEditIndex).Value.ToString
        DetailsView1.Visible = True
        DetailsViewBindData()
    End Sub

    Private Sub DetailsView1_ModeChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DetailsViewModeEventArgs) Handles DetailsView1.ModeChanging
        Select Case e.NewMode
            Case DetailsViewMode.Edit
                Dim lblChId As Label = CType(DetailsView1.FindControl("lblChId"), Label)
                strPeID = lblChId.Text
                DetailsView1.ChangeMode(DetailsViewMode.Edit)
                DetailsViewBindData()

            Case DetailsViewMode.ReadOnly
                'DetailsView1.ChangeMode(DetailsViewMode.ReadOnly)
                DetailsView1.Visible = False
                GridView1.Visible = True
                Response.Redirect("CheckEdit.aspx")
        End Select




    End Sub

    Private Sub DetailsView1_ItemUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DetailsViewUpdateEventArgs) Handles DetailsView1.ItemUpdating
        Dim txtTextBox As TextBox = CType(DetailsView1.FindControl("TextBox1"), TextBox)
        '*** Old PeID ***'
        Dim lblDate0 As Label = CType(DetailsView1.FindControl("lblDate0"), Label)
        strPeID = lblDate0.Text

        '*** PersonelID ***'
       
        Dim txtCheckDate As eWorld.UI.CalendarPopup = CType(DetailsView1.FindControl("txtEditCheckDate"), eWorld.UI.CalendarPopup)

        '*** Position ***'
        Dim txtReTime As DropDownList = CType(DetailsView1.FindControl("txtEditTime"), DropDownList)
        Dim txtTimeAcc As TextBox = CType(DetailsView1.FindControl("txtEditTimeAcc"), TextBox)
        Dim txtStyle As TextBox = CType(DetailsView1.FindControl("txtEditStyle"), TextBox)
        Dim txtPlace As TextBox = CType(DetailsView1.FindControl("txtEditPlace"), TextBox)
        Dim txtCircum As TextBox = CType(DetailsView1.FindControl("txtEditCircum"), TextBox)
        Dim txtFlag As TextBox = CType(DetailsView1.FindControl("txtEditFlag"), TextBox)
        Dim txtChief As DropDownList = CType(DetailsView1.FindControl("txtEditChief"), DropDownList)
        Dim txtOffer As DropDownList = CType(DetailsView1.FindControl("txtEditOffer"), DropDownList)
        Dim txtReceiver As DropDownList = CType(DetailsView1.FindControl("txtEditReceiver"), DropDownList)
        

        'Dim myDate As Date
        'myDate = CalendarPopup1.SelectedDate
        'Dim strdate As String = myDate.ToString.Substring(0, 10)
        'txtCheckDate.Text = strdate
        Sql = "UPDATE TblCheckEvent SET Ch_Id = '" & txtTextBox.Text.Replace("'", "''") & "' " & _
        " ,Ch_DateAccident='" & txtCheckDate.SelectedDate & "' " & _
        " ,Re_Time = '" & txtReTime.SelectedItem.Text & "' " & _
        " ,Ch_TimeAccident = '" & txtTimeAcc.Text & "' " & _
        " ,Ch_StyleEvents = '" & txtStyle.Text & "' " & _
        " ,Ch_Place = '" & txtPlace.Text & "' " & _
        " ,Ch_Circumstance = '" & txtCircum.Text & "' " & _
        " ,Ch_Flag = '" & txtFlag.Text & "' " & _
        " ,Ch_CheifInspector = '" & txtChief.SelectedItem.Text & "' " & _
           " ,Ch_Offer = '" & txtOffer.SelectedItem.Text & "' " & _
            " ,Ch_Receiver = '" & txtReceiver.SelectedItem.Text & "' " & _
        " WHERE Ch_Id = '" & strPeID & "'"

        Cmd = New SqlCommand(Sql, Conn)

        Conn.Open()
        Cmd.ExecuteNonQuery()


        DetailsView1.ChangeMode(DetailsViewMode.ReadOnly)
        DetailsView1.Visible = False
        GridView1.Visible = True
        'GridViewBindData()
        Response.Redirect("CheckEdit.aspx")




    End Sub

End Class

dim Sql as string
Sql = "UPDATE TblCheckEvent SET Ch_Id = '" & txtTextBox.Text.Replace("'", "''") & "' " & _
      " ,Ch_DateAccident='" & txtCheckDate.SelectedDate & "' " & _
      " ,Re_Time = '" & txtReTime.SelectedItem.Text & "' " & _
      " ,Ch_TimeAccident = '" & txtTimeAcc.Text & "' " & _
      " ,Ch_StyleEvents = '" & txtStyle.Text & "' " & _
      " ,Ch_Place = '" & txtPlace.Text & "' " & _
      " ,Ch_Circumstance = '" & txtCircum.Text & "' " & _
      " ,Ch_Flag = '" & txtFlag.Text & "' " & _
      " ,Ch_CheifInspector = '" & txtChief.SelectedItem.Text & "' " & _
         " ,Ch_Offer = '" & txtOffer.SelectedItem.Text & "' " & _
          " ,Ch_Receiver = '" & txtReceiver.SelectedItem.Text & "' " & _
      " WHERE Ch_Id = '" & strPeID & "'"