ASP.Net : Button อยู่ใน Repeater ไม่ทำงานตามคำสั่งเกิดจากอะไรคะ

    <asp:Repeater ID="Repeater2" runat="server">
        <ItemTemplate >
              <asp:Button ID="btn_delimg" CssClass ="btn btn-success btn-xs" 
                  CommandName ="btn_delgallery" CommandArgument='<%#  Eval("dir_gallery") %>' 
                  onclick="ButtonOnRepeaterDelete_Click"
                  runat="server" Text="ลบรูปภาพ"  />
        </ItemTemplate>
    </asp:Repeater>
    <asp:Label ID="Label1" runat="server"  Text ="label1"  ></asp:Label>

    'ใส่ sub นี้ลงไปใน code-behind เดี๋ยว compiler มันจะเชื่อม event นี้ให้เอง
    Sub ButtonOnRepeaterDelete_Click(sender As Object, e As EventArgs) 
          dim button as Button = DirectCast(sender ,Button)
          dim dir_gallery as string = button.CommandArgument

          '............................
          '.........code อะไรก็ว่าไป


    End Sub

Protected Sub UploadThisFile(ByVal upload As FileUpload)
        Dim rndnumber As Random
        Dim number As Integer
        rndnumber = New Random
        number = rndnumber.Next(1, 80000)
        Dim filename As String = number.ToString & "_" & upload.FileName
        If FileUpload1.HasFile Then
            Dim img As String = String.Empty
            Dim bmpImg As Bitmap = Nothing
            Try
                bmpImg = Resize_Image(FileUpload1.PostedFile.InputStream, 960, 960)
                bmpImg.ToString()
                'Server.MapPath("~/Uploads")
                img = Server.MapPath("~/Uploads/") + number.ToString + ".png"
                ins_album(abname:=number.ToString + ".png", dir_name:=number.ToString)
                bmpImg.Save(img, ImageFormat.Jpeg)
            Catch ex As Exception
                Response.Write("Error occured: " & ex.Message.ToString())
            Finally
                img = String.Empty
                bmpImg.Dispose()
            End Try
        End If
    End Sub

Private Function Resize_Image(ByVal streamImage As Stream, ByVal maxWidth As Integer, ByVal maxHeight As Integer) As Bitmap
        Dim originalImage As New Bitmap(streamImage)
        Dim newWidth As Integer = originalImage.Width
        Dim newHeight As Integer = originalImage.Height
        Dim aspectRatio As Double = CDbl(originalImage.Width) / CDbl(originalImage.Height)

        If aspectRatio <= 1 AndAlso originalImage.Width > maxWidth Then
            newWidth = maxWidth
            newHeight = CInt(Math.Round(newWidth / aspectRatio))
        ElseIf aspectRatio > 1 AndAlso originalImage.Height > maxHeight Then
            newHeight = maxHeight
            newWidth = CInt(Math.Round(newHeight * aspectRatio))
        End If
        Return New Bitmap(originalImage, newWidth, newHeight)
    End Function