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Previewing Image in ASP.NET Image Control using C#

, 7 Aug 2012 CPOL
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Previewing Image in ASP.NET Image Control using C#

Introduction

Recently there are so many people asking in forums how to preview an uploaded image before saving it to the database. In this article, let us see how to preview an uploaded image in ASP.NET before saving it to database. Also this we will see how to feed a byte array into an image control. We are going to achieve this using an IhttpHandler.

Using the code

  1. Create a new website. Add a FileUpload control, a button, and an image control.
  2. ASPX code:

    <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>
  3. Now add a button click event for “btnPhotopreview”.
  4. <asp:Button runat="server" OnClick="btnPreview_Click" ID="btnPhotoPreview" Text="Preview" />
  5. 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.
  6. When we add the .ashx file, it will have some code inside it.

    <%@ WebHandler Language="C#" Class="ImageHandler" %>
    
    using System;
    using System.Web;
    
    public class ImageHandler : IHttpHandler {
        
        public void ProcessRequest (HttpContext context) {
            context.Response.ContentType = "text/plain";
            context.Response.Write("Hello World");
        }
     
        public bool IsReusable {
            get {
                return false;
            }
        }
    }

    Just rewrite the code inside processrequest to get the session variable and generate the image.

    In order to use the session variable in the HTTPHandler class we also implement our class from IRequiresSessionState.

    <%@ WebHandler Language="C#" Class="ImageHandler" %>
    
    using System;
    using System.Web;
    
    public class ImageHandler : IHttpHandler, System.Web.SessionState.IRequiresSessionState
    {
        
        public void ProcessRequest (HttpContext context) {
           //Checking whether the imagebytes session variable have anything else not doing anything
    
            if ((context.Session["ImageBytes"]) != null)
            {
                byte[] image = (byte[])(context.Session["ImageBytes"]);
                context.Response.ContentType = "image/JPEG";
                context.Response.BinaryWrite(image);
            }
        }
     
        public bool IsReusable {
            get {
                return false;
            }
        }
    }
  7. Now inside the button click in our page, get the file bytes from the FileUpload control and save it in the session variable.
  8. protected void btnPreview_Click(object sender, EventArgs e)
    {
        Session["ImageBytes"] = PhotoUpload.FileBytes;
        ImagePreview.ImageUrl = "~/ImageHandler.ashx";
    }

Now run the application and browse the image and preview it.

I have attached the complete source code also.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Santhosh Kumar Jayaraman
Software Developer Radiometer
India India
Currently i am trying to learn all about javascripts . I have experience in Microsoft technologies like WPF, WCF, ASPNET, WinForms,Silverlight, VB.NET, C-Sharp, Entity framework,SSRS, LINQ, Extension methods and SQL server. I started with my career in Infosys in the year 2009 and i worked with Trigent, Education First (EF) in the recent years before joining my current company Radiometer.
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Comments and Discussions

 
QuestionMultple Images Pin
Member 1050351423-Mar-15 4:55
memberMember 1050351423-Mar-15 4:55 
GeneralMy vote of 3 Pin
Mohammad Alghanem27-Jan-15 3:44
professionalMohammad Alghanem27-Jan-15 3:44 
QuestionMultiple images in the same page Pin
Member 21609874-Apr-13 1:09
memberMember 21609874-Apr-13 1:09 
GeneralMy vote of 5 Pin
abhi99314-Mar-13 9:41
memberabhi99314-Mar-13 9:41 
GeneralMy vote of 4 Pin
Zan Zan Koe23-Dec-12 7:00
memberZan Zan Koe23-Dec-12 7:00 
GeneralThanks Pin
Member 954329825-Oct-12 10:59
memberMember 954329825-Oct-12 10:59 
Questionif Session["ImageBytes"] returns null Pin
Pritesh Aryan12-Oct-12 6:08
memberPritesh Aryan12-Oct-12 6:08 
AnswerRe: if Session["ImageBytes"] returns null Pin
Santhosh Kumar J12-Oct-12 7:13
memberSanthosh Kumar J12-Oct-12 7:13 
QuestionThank! Pin
goomingi11-Oct-12 19:58
membergoomingi11-Oct-12 19:58 
AnswerRe: Thank! Pin
Santhosh Kumar J11-Oct-12 19:59
memberSanthosh Kumar J11-Oct-12 19:59 
GeneralMy vote of 4 Pin
goomingi11-Oct-12 19:56
membergoomingi11-Oct-12 19:56 
Questionpreview after choosing file Pin
Member 944104919-Sep-12 0:50
memberMember 944104919-Sep-12 0:50 
AnswerRe: preview after choosing file Pin
Santhosh Kumar J19-Sep-12 3:05
memberSanthosh Kumar J19-Sep-12 3:05 
GeneralRe: preview after choosing file Pin
Member 445948429-Oct-12 9:43
memberMember 445948429-Oct-12 9:43 
AnswerRe: preview after choosing file Pin
Sridhar Ch1-Nov-12 0:32
memberSridhar Ch1-Nov-12 0:32 
GeneralRe: preview after choosing file Pin
yugandhar1127-Feb-13 0:13
memberyugandhar1127-Feb-13 0:13 
GeneralMy vote of 4 Pin
Tathagat Verma7-Aug-12 20:00
memberTathagat Verma7-Aug-12 20:00 
GeneralImage upload Pin
shanid3602-Aug-12 21:37
membershanid3602-Aug-12 21:37 
GeneralMy vote of 5 Pin
Carsten V2.029-Jul-12 6:02
memberCarsten V2.029-Jul-12 6:02 
GeneralRe: My vote of 5 Pin
Santhosh Kumar J6-Aug-12 3:50
memberSanthosh Kumar J6-Aug-12 3:50 

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