VB.NET AdRotator.Render方法代码示例

<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomADRotatorRender
    Inherits System.Web.UI.WebControls.AdRotator

    Protected Overrides Sub Render(ByVal writer As System.Web.UI.HtmlTextWriter)
        Dim navigateUrl As String = System.String.Empty
        Dim imageUrl As String = System.String.Empty
        Dim alternateText As String = System.String.Empty

        ' If the value for the Advertisement File is not empty.
        If Me.AdvertisementFile.Length > 0 Then
            ' Get a random ad.
            GetRandomAd(imageUrl, navigateUrl, alternateText)
        End If

        ' Create and render a new HyperLink Web control.
        Dim bannerLink As New System.Web.UI.WebControls.HyperLink
        Dim key As String
        For Each key In Me.Attributes.Keys
            bannerLink.Attributes(key) = Me.Attributes(key)
        Next key
        If Not (Me.ID Is Nothing) AndAlso Me.ID.Length > 0 Then
            bannerLink.ID = Me.ClientID
        End If
        bannerLink.NavigateUrl = navigateUrl
        bannerLink.Target = Me.Target
        bannerLink.AccessKey = Me.AccessKey
        bannerLink.Enabled = Me.Enabled
        bannerLink.TabIndex = Me.TabIndex
        bannerLink.RenderBeginTag(writer)

        ' Create and render a new Image Web control.
        Dim bannerImage As New System.Web.UI.WebControls.Image
        If ControlStyleCreated Then
            bannerImage.ApplyStyle(Me.ControlStyle)
        End If
        bannerImage.AlternateText = alternateText
        bannerImage.ImageUrl = imageUrl
        bannerImage.ToolTip = Me.ToolTip
        bannerImage.RenderControl(writer)
        bannerLink.RenderEndTag(writer)
    End Sub

    Private Sub GetRandomAd(ByRef imageUrl As String, ByRef navigateUrl As String, ByRef alternateText As String)
        ' Default output parameters values to empty string
        imageUrl = System.String.Empty
        navigateUrl = System.String.Empty
        alternateText = System.String.Empty

        ' Get the Ads from an XML file.
        Dim dataSet As New System.Data.DataSet
        Dim physicalPath As String = MapPathSecure(Me.AdvertisementFile)
        dataSet.ReadXml(physicalPath, System.Data.XmlReadMode.InferSchema)

        ' If Ads were found in the XML File.
        Dim totalAds As Integer = dataSet.Tables(0).Rows.Count
        If totalAds > 0 Then

            ' Select a random Ad.
            Dim randomNumber As New System.Random
            Dim selectedAdIndex As Integer = randomNumber.Next(totalAds)

            ' Output the random Ad's values.
            imageUrl = dataSet.Tables(0).Rows(selectedAdIndex).ItemArray(0).ToString()
            navigateUrl = dataSet.Tables(0).Rows(selectedAdIndex).ItemArray(1).ToString()
            alternateText = dataSet.Tables(0).Rows(selectedAdIndex).ItemArray(2).ToString()
        End If
    End Sub
End Class