Previewing Image in ASP.NET Image Control using VB.NET

• Download ImageViewerinVB.zip - 195.5 KB

This is an alternative for "Previewing Image in ASP.NET Image Control"

Introduction

I have already published a tip how to preview the image in ASP.NET image control using C# language. Recently many of them asked me how to achieve this in VB.Net. I asked them to use code converter tool but still many didn't get the appropriate code. So i decided to explain how to achieve the same using VB.NET in this alternative tip

Using the Code

1. Create a new website. Add a FileUpload control, a button, and an image control.

ASPX code:

XML

<table>
    <tr>
        <td class="style3">
            <asp:Label ID="Label1" runat="server" Text="Photo upload" />
        </td>
        <td class="style4">
            <asp:FileUpload runat="server" ID="PhotoUpload" />
        </td>
        <td class="style4">
            <asp:Button runat="server" ID="btnPhotoPreview" Text="Preview" />
        </td>
        <td class="style1">
            <asp:Image runat="server" ID="ImagePreview" Height="164px" Width="125px" />
        </td>
    </tr>
</table>

2. Now add a button click event for btnPhotopreview.
   ASP.NET

   <asp:Button runat="server" OnClick="btnPreview_Click" ID="btnPhotoPreview" Text="Preview" />

3. We have to add a handler class in order to show the image. We are going to pass the session variable for FileBytes for the upload control. In the new handler class, get the session variable and generate the image and the main difference between C# and vb comes here in this part in handling session variables. 
   VB

   Imports System.Web
   Imports System.Web.Services
   
   Public Class Handler1
       Implements System.Web.IHttpHandler, System.Web.SessionState.IRequiresSessionState
   
       Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
   
           If (context.Session("ImageBytes")) IsNot Nothing Then
               Dim image As Byte() = DirectCast(context.Session("ImageBytes"), Byte())
               context.Response.ContentType = "image/JPEG"
               context.Response.BinaryWrite(image)
           End If
   
       End Sub
   
       ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
           Get
               Return False
           End Get
       End Property
   
   End Class

4. Now in the button click pass the byte[] in session variable.

Protected Sub btnPhotoPreview_Click(sender As Object, e As EventArgs) Handles btnPhotoPreview.Click

        Session("ImageBytes") = PhotoUpload.FileBytes
        ImagePreview.ImageUrl = "~/Handler1.ashx"
    End Sub

I have attached the source code. It is written in Visual studio 2012, so the solution might not be work with few of your machines. But you can check the class files.