I have a table in a database that contains all kind of attachments, images, pdf, excel, and other formats. creating an application is not an option, so I googled other options and I found this related question that mentioned LINQPad I downloaded it but I still do not know how exactly it works. Anyone please explain that to me? I can query the attachments using sql query but not sure how to dump them and preview them via the mentioned tools.
Following on from Dan's answer, once you have the data context set up you can dump the images from the database. I use this snippet for checking an image I've written to the database, you should be able to edit as required to match your scenario:-
var ii = ItemImages.Where (v => v.Id == 10).FirstOrDefault();
using (var ms = new MemoryStream(ii.Image.ToArray()))
{
System.Drawing.Image.FromStream(ms).Dump();
}