Atlas Tutorial: Creating an AJAX Scribble Application

<%@ WebHandler Language="VB" Class="ScribbleImage" %>

Imports System
Imports System.Web
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.IO

Public Class ScribbleImage : Implements IHttpHandler, System.Web.SessionState.IRequiresSessionState
    
    Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
        context.Response.ContentType = "image/png"
        context.Response.Cache.SetNoStore()
        context.Response.Cache.SetCacheability(HttpCacheability.NoCache)
        context.Response.Cache.SetExpires(DateTime.Now)
        context.Response.Cache.SetValidUntilExpires(False)
        Dim bmp As Bitmap = CType(context.Session.Item("Image"), Bitmap)

        SyncLock (bmp)
            Using ms As MemoryStream = New MemoryStream()
                bmp.Save(ms, ImageFormat.Png)
                ms.Flush()
                context.Response.BinaryWrite(ms.GetBuffer())
            End Using
        End SyncLock
    End Sub
 
    Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
        Get
            Return False
        End Get
    End Property

End Class