This ASP.NET Spam Safe Link control can show an e-mail
address as a link on a web page without the risk of the address being captured by
It's an e-mail link. But is it safe?
If you want to show an e-mail address on a web page, you usually insert some HTML
code like this:
Unfortunately, this type of code can easily be captured by spammers, and soon your
address will be distributed on cd's to bad people. Your inbox will be full of unsolicited
not supported by the client, you can still provide the visitor with an image that
shows the address.
Because this situation is recurring on web pages all the time, I decided to create
a user control that deals with it. It will show the mail address just as you would
expect it, but it will be spam-safe.
From now on, you can just drop the SpamSafeLink control on your ASP.NET page, set
one or two properties, and the control will take care of the rest.
Installing the control
Just unzip the source files and copy both files "SpamSafeLink.ascx" and
"image.aspx" to any folder in your website.
Using the control
In your editor (Web Matrix, C# Builder, Visual Studio, ...), drag the file "SpamSafeLink.ascx"
onto your page, where you want the link to appear.
If you use another editor, you can add the control manually. Add this directive
on top of the page:
<%@ Register TagPrefix="rw" TagName="SpamSafeLink" Src="SpamSafeLink.ascx" %>
Then, add a tag like this in your HTML code where you want the e-mail link to be
<rw:SpamSafeLink id="SpamSafeLink1" Address="firstname.lastname@example.org" Text="Contact"
BgColor="White" LinkColor="Blue" Size="12" FontName="Verdana" runat="server">
Next, make sure you use the appropriate settings.
Use the demo page "demo.aspx" as a sample showing you how the SpamSafeLink
temporarily in your browser. Look here for
you can have your browser prompt you every time.
These are the control properties that you can set:
- Address (String)
This is the most important property. Enter the e-mail address that you want to use
caption, but it will not work as a link.
- Text (String)
This is the caption that will be displayed as a link. Only set this property when
you want a caption that is NOT the mail address.
When omitted, the Address property will be used instead.
- BgColor (Color)
This is the background color for the image (white by default). When the client supports
- LinkColor (Color)
This is the text color for the image (blue by default). When the client supports
- Size (Integer)
this property is ignored.
- FontName (String)
The name of the font face for the image ("Verdana" by default). When the
but it will not work as a link.
How it works
The control simply splits the address in 2 parts, using the ampersand as the separator.
In that way, a spam bot scouting for addresses in your page will be confused. It's
still a link, but the real address is not easily readable in the page's HTML.
<img src="<%=GetImageURL()%>" />
The function GetImageURL() calls an ASP.NET file that will create the image on-the-fly:
Private Function GetImageURL() As String
Return "image.aspx?address1=" & _address1 & "&address2=" & _address2 & _
"&linkcolor=" & _LinkColor.ToArgb() & "&bgcolor=" & _BgColor.ToArgb() & _
"&size=" & _Size & "&FontName=" & _FontName
The address, caption, colors, size and font are taken from the user control's properties,
and passed as GET query parameters. This block calls the code in "image.aspx",
which will create a GIF image that just displays the e-mail address. It will not
work as a clickable link in this case.
In order to save processor time, the cache duration time is set very high.
<%@ Page Language="VB" %>
<%@ OutputCache Duration="3600" VaryByParam="Address1;Address2;size;bgcolor;linkcolor;FontName" %>
<%@ import Namespace="System.Drawing" %>
<%@ import Namespace="System.Drawing.Imaging" %>
<%@ import Namespace="System.Drawing.Drawing2D" %>
Sub Page_Init( sender As Object, e As EventArgs)
Response.ContentType = "image/gif"
Dim FontName As String = Request.QueryString("FontName")
Dim Address As String = Request.QueryString("Address1") & "@" & Request.QueryString("Address2")
Dim objFont As Font = New Font(FontName, CInt(Request.QueryString("size")))
Dim objBitmapTemp As Bitmap= New Bitmap(1, 1)
Dim objGraphicsTemp As Graphics = Graphics.FromImage(objBitmapTemp)
Dim ImageSize As SizeF = objGraphicsTemp.MeasureString(Address,objFont)
Dim objBitmap As Bitmap= New Bitmap(Convert.ToInt32(ImageSize.width), Convert.ToInt32(ImageSize.height))
Dim objGraphics As Graphics = Graphics.FromImage(objBitmap)
Dim BgBrush = New SolidBrush(Color.FromArgb(Request.QueryString("bgcolor")))
Dim TextBrush = New SolidBrush(Color.FromArgb(Request.QueryString("linkcolor")))
objGraphics.FillRectangle(BgBrush, 0, 0, ImageSize.width, ImageSize.height)
objGraphics.DrawString(Address, objFont, TextBrush, 0, 0)
<!-- no HTML content -->
Here are some ideas for future improvement:
- Extract the font face, color and size from a style sheet (if the page uses one).
- Use relative sizes instead of absolute ones.
- Convert it to a full custom control.
If anyone decides to extend this, or has any comments or questions then it would
be great to hear from you.
Points of interest
- user controls
- using GDI+ graphics in ASP.NET
5/8/2004: Release of Version 1.0.