1Imports System
 2Imports System.Web
 3Imports System.Drawing
 4
 5/**/''' <summary>
 6''' Captcha image stream HttpModule. Retrieves CAPTCHA objects from cache, renders them to memory, 
 7''' and streams them to the browser.
 8''' </summary>
 9''' <remarks>
10''' You *MUST* enable this HttpHandler in your web.config, like so:
11'''
12'''      &lt;httpHandlers&gt;
13'''          &lt;add verb="GET" path="CaptchaImage.aspx" type="WebControlCaptcha.CaptchaImageHandler, WebControlCaptcha" /&gt;
14'''      &lt;/httpHandlers&gt;
15'''
16''' Jeff Atwood
17''' http://www.codinghorror.com/
18'''</remarks>
19Public Class CaptchaImageHandlerClass CaptchaImageHandler
20    Implements IHttpHandler
21
22    Public Sub ProcessRequest()Sub ProcessRequest(ByVal context As System.Web.HttpContext) Implements System.Web.IHttpHandler.ProcessRequest
23        Dim app As HttpApplication = context.ApplicationInstance
24
25        '-- get the unique GUID of the captcha; this must be passed in via the querystring
26        Dim guid As String = app.Request.QueryString("guid")
27        Dim ci As CaptchaImage = Nothing
28
29        If guid <> "" Then
30            If String.IsNullOrEmpty(app.Request.QueryString("s")) Then
31                ci = CType(HttpRuntime.Cache.Get(guid), CaptchaImage)
32            Else
33                ci = CType(HttpContext.Current.Session.Item(guid), CaptchaImage)
34            End If
35
36        End If
37
38        If ci Is Nothing Then
39            app.Response.StatusCode = 404
40            context.ApplicationInstance.CompleteRequest()
41            Return
42        End If
43
44        '-- write the image to the HTTP output stream as an array of bytes
45        Dim b As Bitmap = ci.RenderImage
46        b.Save(app.Context.Response.OutputStream, Drawing.Imaging.ImageFormat.Jpeg)
47        b.Dispose()
48        app.Response.ContentType = "image/jpeg"
49        app.Response.StatusCode = 200
50        context.ApplicationInstance.CompleteRequest()
51    End Sub
52
53    Public ReadOnly Property IsReusable()Property IsReusable() As Boolean Implements System.Web.IHttpHandler.IsReusable
54        Get
55            Return True
56        End Get
57    End Property
58
59End Class