Dynamically Rendering asp:Image from BLOB entry in ASP.NET

Question

What I want to achieve is this. I want to give the user the ability to upload an image file, store the image in BLOB in SQL Server, and then use this image as a logo in other pages of the site.

I have done this by using

   Response.Clear();
   Response.ContentType = "image/pjpeg";
   Response.BinaryWrite(imageConents);
   Response.End();

but to do this, I use a User control in the place where I want to show the image. I want to do it if possible using an asp:Image control, or even a pure old html image control. Is this possible?

Answer 1

Add a 'Generic Handler' to your web project, name it something like Image.ashx. Implement it like this:

public class ImageHandler : IHttpHandler
{

    public void ProcessRequest(HttpContext context)
    {
        using(Image image = GetImage(context.Request.QueryString["ID"]))
        {    
            context.Response.ContentType = "image/jpeg";
            image.Save(context.Response.OutputStream, ImageFormat.Jpeg);
        }
    }

    public bool IsReusable
    {
        get
        {
            return true;
        }
    }
}

Now just implement the GetImage method to load the image with the given ID, and you can use

<asp:Image runat="server" ImageUrl="~/Image.ashx?ID=myImageId" /> 

to display it. You might want to think about implementing some form of caching in the handler too. And remember if you want to change the image format to PNG, you need to use an intermediate MemoryStream (because PNGs require a seekable stream to be saved).