Hello,

How to show processing image when a page is loaded or postback in Vb of asp net

I had create the Chart Applications in Vb.Net, I would like to Show processing image when a page is loaded or postback  when the user press generate Chart Button.

Here my Coding of Generate Chart:

    Protected Sub btn_Rate_Click(sender As Object, e As EventArgs) Handles btn_Rate.Click
        If String.IsNullOrEmpty(Label45.Text) Then
            Dim message As String = "Select Period End "
            Dim sb As New System.Text.StringBuilder()
            sb.Append("<script type = 'text/javascript'>")
            sb.Append("window.onload=function(){")
            sb.Append("alert('")
            sb.Append(message)
            sb.Append("')};")
            sb.Append("</script>")
            ClientScript.RegisterClientScriptBlock(Me.GetType(), "alert", sb.ToString())
            DropDownList5.BackColor = Color.Red
            DropDownList5.ForeColor = Color.Yellow
            DropDownList6.BackColor = Color.Red
            DropDownList6.ForeColor = Color.Yellow
            DropDownList9.BackColor = Color.Red
            DropDownList9.ForeColor = Color.Yellow
            DropDownList10.BackColor = Color.Red
            DropDownList10.ForeColor = Color.Yellow
            DropDownList12.BackColor = Color.Red
            DropDownList12.ForeColor = Color.Yellow
            DropDownList16.BackColor = Color.Red
            DropDownList16.ForeColor = Color.Yellow
            DropDownList17.BackColor = Color.Red
            DropDownList17.ForeColor = Color.Yellow
        Else
            If DropDownList2.SelectedIndex <= 0 And DropDownList13.SelectedIndex <= 0 Then
                btn_Int.Visible = False
                DropDownList2.BackColor = Color.Red
                DropDownList2.ForeColor = Color.Yellow
                Dim message As String = "Please Select Department"
                Dim sb As New System.Text.StringBuilder()
                sb.Append("<script type = 'text/javascript'>")
                sb.Append("window.onload=function(){")
                sb.Append("alert('")
                sb.Append(message)
                sb.Append("')};")
                sb.Append("</script>")
                ClientScript.RegisterClientScriptBlock(Me.GetType(), "alert", sb.ToString())
            Else
                DropDownList2.BackColor = Color.White
                DropDownList2.ForeColor = Color.Black
                btn_Int.Visible = True
                If String.IsNullOrEmpty(Label22.Text) Then
                    Label39.Text = Label40.Text
                Else
                    System.Threading.Thread.Sleep(5000)
                    Label39.Text = Label40.Text & Label41.Text
                    Label37.Visible = True
                    Label48.Visible = True
                    Label49.Visible = False
                    Label52.Text = String.Empty
                    Label54.Text = String.Empty
                    Label37.Text = Label38.Text & " Rate  " & " in " & Label39.Text
                    BindRateChart()
                    btn_Print.Visible = True
                    RateChart.Visible = True


                    If RadioButtonList1.SelectedIndex = 3 Then
                        Label37.Text = "12-Month Rolling Trend of " & Label38.Text & " Rate  " & " in " & Label39.Text
                        Label48.Text = ""
                    Else
                        Label37.Text = Label38.Text & " Rate  " & " in " & Label39.Text
                        Label48.Text = "From" & " " & Label42.Text & " " & "to" & " " & Label45.Text
                    End If
                End If
            End If
        End If
    End Sub
    Private Sub BindIntChart()
        Label58.Text = "Number of " & Label59.Text
        RateChart.Visible = True
        Dim dtInt As System.Data.DataTable = New System.Data.DataTable("dtInts")
        For Each cell As TableCell In gvInt.HeaderRow.Cells
            dtInt.Columns.Add(cell.Text.Trim())
        Next
        For Each row As GridViewRow In gvInt.Rows
            dtInt.Rows.Add()
            Dim k As Integer = 0
            For k = 0 To row.Cells.Count - 1
                dtInt.Rows(row.RowIndex)(k) = row.Cells(k).Text.Trim()
            Next
        Next

        Dim departments As List(Of String) = New List(Of String)()
        departments = (From p In dtInt.AsEnumerable()
                        Select p.Field(Of String)("Department")).Distinct().ToList()

        If RateChart.Series.Count() = 1 Then
            RateChart.Series.Remove(RateChart.Series(0))
        End If
        Dim i As Integer = 0
        For i = 0 To departments.Count - 1 Step 1
            Dim x As String() = (From p In dtInt.AsEnumerable()
                                    Order By p.Field(Of String)("Period_Shown")
                                    Select p.Field(Of String)("Period_Shown")).Distinct().ToArray()

            Dim y As List(Of Decimal) = New List(Of Decimal)()
            Dim j As Integer = 0
            For j = 0 To x.Length - 1 Step 1
                Dim numInt As Decimal = (From p In dtInt.AsEnumerable()
                                            Where p.Field(Of String)("Department") = departments(i) _
                                                AndAlso p.Field(Of String)("Period_Shown") = x(j)
                                            Order By p.Field(Of String)("Period_Shown")
                                            Select Convert.ToDecimal(p.Field(Of String)("Num_Int"))).FirstOrDefault()
                y.Add(numInt)
            Next
            RateChart.Series.Add(New System.Web.UI.DataVisualization.Charting.Series(departments(i)))
            RateChart.Series(departments(i)).IsValueShownAsLabel = False
            RateChart.Series(departments(i)).BorderWidth = 3
            RateChart.Series(departments(i)).ChartType = SeriesChartType.Line
            RateChart.Series(departments(i)).Points.DataBindXY(x, y)
            RateChart.Series(departments(i)).MarkerStyle = MarkerStyle.Cross
            RateChart.Series(departments(i)).MarkerSize = 6
            RateChart.Series(departments(i)).MarkerColor = Color.Gray
        Next
        RateChart.Legends.Add("Default")
        RateChart.Legends(0).Docking = Docking.Bottom
        RateChart.Legends(0).IsTextAutoFit = True
        RateChart.Legends(0).Alignment = System.Drawing.StringAlignment.Center
        RateChart.Legends(0).Enabled = True
        RateChart.ChartAreas(0).AxisX.Interval = 1
        RateChart.ChartAreas(0).AxisX.Title = "Period"
        RateChart.ChartAreas(0).AxisX.TitleFont = New System.Drawing.Font("Times New Roman", 12.0!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, 0)
        RateChart.ChartAreas(0).AxisX.TitleForeColor = System.Drawing.Color.Red
        RateChart.ChartAreas(0).AxisX.MajorGrid.LineDashStyle = DataVisualization.Charting.ChartDashStyle.Dot
        RateChart.ChartAreas(0).AxisX.MajorGrid.LineColor = System.Drawing.Color.DimGray
        RateChart.ChartAreas(0).AxisX.MinorGrid.LineDashStyle = DataVisualization.Charting.ChartDashStyle.Dot
        RateChart.ChartAreas(0).AxisX.MinorGrid.LineColor = System.Drawing.Color.DimGray
        RateChart.ChartAreas(0).AxisY.Title = Label58.Text
        RateChart.ChartAreas(0).AxisY.TitleFont = New System.Drawing.Font("Times New Roman", 12.0!, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, 0)
        RateChart.ChartAreas(0).AxisY.TitleForeColor = System.Drawing.Color.Red
        RateChart.ChartAreas(0).AxisY.TitleAlignment = System.Drawing.StringAlignment.Far
        RateChart.ChartAreas(0).AxisY.TextOrientation = TextOrientation.Rotated270
        RateChart.ChartAreas(0).AxisY.MajorGrid.LineDashStyle = DataVisualization.Charting.ChartDashStyle.Dot
        RateChart.ChartAreas(0).AxisY.MajorGrid.LineColor = System.Drawing.Color.DimGray
        RateChart.ChartAreas(0).AxisY.MinorGrid.LineDashStyle = DataVisualization.Charting.ChartDashStyle.Dot
        RateChart.ChartAreas(0).AxisY.MinorGrid.LineColor = System.Drawing.Color.White
        btn_Download_RD.Visible = False
        btn_Download_RD0.Visible = True
    End Sub