SPMetal getting picture thumbnail url

Question

I am making a custom web part and need to be able to pull a picture thumbnail from a picture library. I am using SPMetal generated classes and don't see a way to do this.

It seems that thumbnails are put into a folder /_t and are changed to .jpg files with their extension appended with _ext.jpg but I was hoping that this value would exist somewhere.

So my question is how do I get the thumbnail source for a picture in a library? Prefer to use SPMetal classes (Even if I have to extend the class it is ok).

Answer 1

To fix this issue I had to extend the classes generated by SPMetal. http://zimmergren.net/technical/extending-the-linq-to-sharepoint-context-to-allow-additional-fields-and-properties-in-your-queries is a pretty good resource for this except for the fact that I had to remove the namespace to get it to work (I'm not entirely sure why though. Can only assume it is because the generated classes have no namespace).

The MapFrom method is what caused me problems. Essentially it seemed like the the listitem being passed to MapFrom doesn't have all the fields loaded and I got an exception stating the value is not withing the expected range. The key to solving this was to add the CustomMapping attribute to get it to load the fields that I need. To solve the problem I used the following code

    public string ThumbnailUrl { get; set; }

    public string PictureUrl { get; set; }
    [CustomMapping(Columns = new[] { "EncodedAbsThumbnailUrl", "EncodedAbsUrl" })]
    public void MapFrom(object listItem)
    {
        var item = listItem as SPListItem;
        if (item != null)
        {
            ThumbnailUrl = item["EncodedAbsThumbnailUrl"].ToString();
            PictureUrl = item["EncodedAbsUrl"].ToString();
        }
    }

Answer 2

The thumbnail is also available via a particular field AlternateThumbnailUrl its internal name. Try adding that to your SPMetal as being an out-of-the-box field it should work.