เกี่ยวกับ การ update ข้อมูลครับ ปัญหาดังนี้ คือผมใช้ Datalist ในการ แสดงข้อมูล แล้วใช้ update command

Imports System.Data
Imports System.Data.SqlClient
Partial Class webboard
    Inherits System.Web.UI.Page
    Dim conn As SqlConnection
    Dim cmd As SqlCommand

    Public Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim con_db As String = "server=TAK\SQLEXPRESS; uid=sa; pwd=1234; database=web;"
        conn = New SqlConnection(con_db)
        conn.Open()
        Dim check_admin As String = "select * from admin WHERE admin_user ='" & Session("admin_user") & "' and admin_pass ='" & Session("admin_pass") & "'"
        cmd = New SqlCommand(check_admin, conn)
        Dim chk As Integer = cmd.ExecuteScalar
        If chk >= 1 Then
            category_admin()
        Else
            Response.Write("no")
        End If
    End Sub

    Sub category_admin()

        Dim sql As String = "select * from category"
        cmd = New SqlCommand(sql, conn)
        Dim reader As SqlDataReader
        reader = cmd.ExecuteReader
        DataList1.DataSource = reader
        DataList1.RepeatColumns = "3"
        DataList1.DataBind()
        reader.Close()
        reader = Nothing


    End Sub

    Public Sub Datalist1_ItemDataBound(ByVal sender As Object, ByVal e As DataListItemEventArgs) Handles DataList1.ItemDataBound
        Dim icon_category As Image = CType(e.Item.FindControl("icon_category"), Image)
        If Not IsNothing(icon_category) Then
            icon_category.ImageUrl = e.Item.DataItem("icon_category_resize")
        End If

        Dim lbname_category As Label = CType(e.Item.FindControl("lbname_category"), Label)
        If Not IsNothing(lbname_category) Then
            lbname_category.Text = e.Item.DataItem("category_name")
        End If

        Dim lbdetail_category As Label = CType(e.Item.FindControl("lbdetail_category"), Label)
        If Not IsNothing(lbdetail_category) Then
            lbdetail_category.Text = e.Item.DataItem("category_detail")
        End If

        Dim edit As LinkButton = CType(e.Item.FindControl("edit"), LinkButton)
        If Not IsNothing(edit) Then
            edit.CommandName = "Edit"
            'edit.PostBackUrl = "webboard.aspx?category_id=" & e.Item.DataItem("category_id")
        End If

        Dim img_edit As Image = CType(e.Item.FindControl("img_edit"), Image)
        If Not IsNothing(img_edit) Then
            img_edit.ImageUrl = "/image/Olympiad Icon 13.png"
        End If

        Dim lbid_category As Label = CType(e.Item.FindControl("lbid_category"), Label)
        If Not IsNothing(lbid_category) Then
            lbid_category.Text = e.Item.DataItem("category_id")
        End If

        Dim bt_update As LinkButton = CType(e.Item.FindControl("bt_update"), LinkButton)
        If Not IsNothing(bt_update) Then
            bt_update.CommandName = "Update"
        End If
    End Sub

    Public Sub Datalist1_EditCommand(ByVal sender As Object, ByVal e As DataListCommandEventArgs) Handles DataList1.EditCommand
        DataList1.EditItemIndex = e.Item.ItemIndex
        category_admin()
    End Sub

    Public Sub Datalist1_UpdateCommand(ByVal sender As Object, ByVal e As DataListCommandEventArgs) Handles DataList1.UpdateCommand
        Dim txname As TextBox = CType(e.Item.FindControl("txname"), TextBox)
        Dim lbid_category As Label = CType(e.Item.FindControl("lbid_category"), Label)

        Dim up_category As String = "UPDATE category SET category_name = @name WHERE category_id ='1'"
         cmd = New SqlCommand(up_category, conn)
        cmd.Parameters.AddWithValue("name", txname.Text)

        cmd.ExecuteNonQuery()


    End Sub

    Public Sub btlogin_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btlogin.Click
        Dim sql As String = "select * from admin WHERE admin_user ='" & tbxuser.Text & "' AND admin_pass='" & tbxpass.Text & "' "
        cmd = New SqlCommand(sql, conn)
        Dim check_admin As Integer = cmd.ExecuteScalar
        If check_admin >= 1 Then
            Session("admin_user") = tbxuser.Text
            Session("admin_pass") = tbxpass.Text
            Page.RegisterClientScriptBlock("OnUnLoad", "<script>window.location='webboard.aspx'</script>")
        Else
            Page.RegisterClientScriptBlock("OnClick", "<script>alert('ข้อมูลไม่ถูกต้อง')</script>")
            Page.RegisterClientScriptBlock("OnUnLoad", "<script>window.location='webboard.aspx'</script>")

        End If
    End Sub
End Class