Retrieving an image from database with Linq to SQL

Question

In my database I have stored images in the "image" data type, showing up as a binary code. I now want to retrieve all images from one column and diplay them on a asp.net page with C#.

databaseDataContext db = new databaseDataContext();

    var images = from Picture p in db.Pictures
                 select p.pictureThumb;

then I use this:

    foreach (Picture p in images)
    {
        galleryImages.Controls.Add(p);
    }

But that doesn't work because Binary can't be converted to Picture. I have Googled this and found that I have to cast to Byte and then to image? I can't find examples on how to do that though.

Solution

This should do it:

databaseDataContext db = new databaseDataContext();

var images = from p in db.Pictures
             select Image.FromStream(new MemoryStream(p.pictureThumb.ToArray());
foreach (Image image in images)
{
    galleryImages.Controls.Add(image);
}

Note that Image.FromStream takes ownership of the stream - it's only a MemoryStream anyway, but do make sure that you dispose of the image, for various reasons.

---

EDIT: Ah... I hadn't realised that this was for ASP.NET. That makes things harder - because the HTML is going to contain URLs, and then you'll need to be able to fetch the data later.

Does a picture have an ID of some kind? If so, fetch that instead of the actual data, and then set up a URL which is able to serve any thumbnail based on the ID (by fetching it from the database and just serving it with an appropriate content type).

Comments

[Bam Bám]

Thanks, that took care of a lot of problems. I have some issues with the loop though, "The best overloaded method match [...] has some invalid arguments". galleryImages refers to a PlaceHolder, but the other possibilities (Literal, Image, etc) give the same error. PLUS the Add(image) tells me "cannot convert from 'System.Drawing.Image' to 'System.Web.UI.Control'". I bet it's fairly obvious I'm very inexperienced with .NET :o

[Bam Bám]

That did it :) Retrieve the pictureID from the database, then use getImage.aspx.cs to extract the actual imagedata. Use ContentType = "image/jpeg"; and BinaryWrite. Thanks Jon!

[Jon Skeet]

Cool - for someone who claims to be "very inexperienced" that was a really quick turnaround :)

[Bam Bám]

I recognized a lot of things I already read on my Googlequest and realized how to use them :)