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Rendering an Image from a blob using an httpHandler

So I've written before on how to upload a file to a blob in Oracle, but I haven't written about how to retrieve it. In this post I am specifically talking about images in this post but you can change out the MIME type and it would work the same.

I am going to show you how to use an IHTTPHandler in order to show your image. I used this for reference.

So add to your project a new generic handler. It will pre-populate a few methods, and basically you just add to them. See my code below

Public Class ImageHandler
   Implements System.Web.IHttpHandler

   Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
       If context.Request.QueryString("id") IsNot Nothing Then
           Dim id As Integer = CInt(context.Request.QueryString("id"))
           Dim blob As Byte()
           blob = getImage(id)
           If blob IsNot Nothing Then
               context.Response.Clear()
               context.Response.ContentType = "image/pjpeg"
               context.Response.BinaryWrite(blob)
               context.Response.End()
           End If
       End If
   End Sub

   ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
       Get
           Return True
       End Get
   End Property


   Private Function getImage(ByVal ID As Integer) As Byte()
       'Select blob from the db
   End Function
End Class

So after you have added this to your project you are ready to use it. There are many ways to do this, but I used an .Net image control. Either in the code behind or at design time, I defined the URL in the code behind when I bound the rest of the stuff on my page, but basically all you to have to do is link to the HttpHandler, and give it a query string with the ID you want. Example below

    Me.imgProductImage.ImageUrl = "~/imagehandler.ashx?id=" & D

Labels: .NET

posted by Tom Becker at 1/14/2009 | 1 Comments