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POmodel an abstract base class and subclasses in a database
 

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    <p>I have 4 subclasses: <code>Video</code>, <code>Image</code>, <code>Note</code>, and <code>Form</code>. Each one contains different types of data. For example, the <code>Image</code> class contains a path to the image file on disk and image properties, and the <code>Form</code> class contains the form field values. The common element between each item, however, is the GPS coordinates and heading, so I have the following abstract base class:</p> <pre><code>public abstract class Content { public float? Latitude { get; set; } public float? Longitude { get; set; } public float? Heading { get; set; } } </code></pre> <p>However, where I get hazy is on how to model this in a database. Currently I have a table called <code>Events</code> (for the sake of example, let's say an event is a birthday party) and 4 tables (<code>Videos</code>, <code>Images</code>, <code>Notes</code>, and <code>Forms</code>). Each table has a foreign key linking back to <code>Events</code>' primary key.</p> <p>Using LINQ-to-SQL, I get 5 classes for each table. This is fine if I only want one type of data, for example <code>Event.Images</code>, but what I want to do is count the total number of 'contents' an <code>Event</code> has and get the GPS coordinates. I can wing the count easy enough by just using <code>Event.Images.Count() + Event.Videos.Count() + ...</code>, but I can't do the same for the GPS coordinates. Is there some way I can model the database so that I can use a base class for every item and still be able to get the individual strongly-typed item when I need to see its data?</p>
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