Using the FlexCel ASP viewer component (VB.Net / netframework)

Note

This demo is available in your FlexCel installation at <FlexCel Install Folder>\samples\vb\VS2022\netframework\25.Printing and Exporting\50.ASP.NET HTML Viewer and also at https:​//​github.​com/​tmssoftware/​TMS-​FlexCel.​NET-​demos/​tree/​master/​vb/​VS2022/​netframework/​Modules/​25.​Printing and Exporting/50.ASP.NET HTML Viewer

Overview

A simple example on how to use the component FlexCelAspViewer to display xls files as html in a web browser.

Note

This demo does not run from MainDemo and it needs **.NET 2.0 or newer.

In order to run this demo, open the website from Visual Studio 2005 or newer, by doing: Menu->File->Open->Website

and pointing to the Modules\25.Printing and Exporting\50.ASP.NET HTML Viewer folder.

Concepts

• In this demo we will use .TemporaryFiles to create the images. This will create all images as GUIDs in the "images" folder. Images older than 15 minutes will be deleted when a new page is requested, and there is an "overflow guard" that prevents having more than 5000 images in the images folder.

• If you wanted to use HttpHandlers to return the images, you would need to add the following lines to web.config:

    <httpHandlers>
    <add verb="*" path="flexcelviewer.ashx"
      type="FlexCel.AspNet.UniqueTemporaryFilesImageHandler,FlexCel.AspNet"/>
    </httpHandlers>
  

This has already been done in the example, so you just need to switch the image mode to use UniqueTemporaryFiles.

• In order to delete the temporary images once the timeout has happened, we use ImageTimeout and MaxTemporaryImages. Make sure you have rights to delete images in the image folders for this to work. You could also manually delete the images with a script on the server.

• FlexCelAspViewer is great for small sites, but due to the way it handles images, (make sure you read the [

  ) it might not scale enough if you do not provide a custom image handler. ](~/guides/html-exporting-guide.md# -----it-might-not-scale-enough-if-you-do-not-provide --a-custom-image-handler )

Files

Default.aspx.vb

Imports System
Imports System.Data
Imports System.Configuration
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.UI.HtmlControls

Imports FlexCel.Core
Imports FlexCel.XlsAdapter
Imports FlexCel.Render
Imports FlexCel.AspNet

Partial Public Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        Dim xls As New XlsFile()

        Dim DefaultFile As String = Server.MapPath("~/default.xls")
        If IsPostBack Then
            If Uploader.HasFile Then
                xls.Open(Uploader.FileContent)
            Else
                xls.Open(DefaultFile)
            End If
        Else
            xls.Open(DefaultFile)
        End If

        Viewer.HtmlExport.ImageNaming = TImageNaming.Guid
        Viewer.HtmlExport.Workbook = xls
        Viewer.RelativeImagePath = "images"
        Viewer.HtmlExport.FixIE6TransparentPngSupport = True 'This is only needed if you are using IE and there are transparent png files.
        Viewer.ImageExportMode = TImageExportMode.TemporaryFiles

    End Sub
End Class