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copied!<p>Strictly speaking, any object that implements <code>IDisposable</code> and whose scope is limited to that function should be within a <code>using</code> block. The <code>IDisposable</code> interface exists to allow classes that deal with unmanaged resources (database connections, file handles, window handles, etc.) to dispose of these resources in a timely, deterministic fashion.</p> <p>There are, in general, three ways in which an <code>IDisposable</code> object is used within a class:</p> <ol> <li>The object is both created and no longer needed within the scope of a single method call. This is quite common, and is when <code>using</code> can (and should) be used.</li> <li>The object is created by the class (or is passed to the class), and its lifetime extends beyond the scope of a single method call but not beyond the life of the class. For example, your class creates a <code>Stream</code> and needs to use it over the lifetime of the object. In this case, your class should implement <code>IDisposable</code> itself and dispose of the object(s) that you own when your own <code>Dispose</code> method is called. An example of this would be something like <code>System.IO.StreamWriter</code></li> <li>The object is passed to the class, but the class doesn't "own" it. This means that the <code>IDisposable</code> object's usable lifetime is beyond the scope of a single method call, and may be beyond the lifetime of your object. In this case, someone else must be responsible for calling <code>Dispose</code>.</li> </ol> <p>The first case is the most common that you'll encounter, which is why the <code>using</code> block exists. It takes care of ensuring that the object will be disposed of, even in the case of an exception.</p> <p>Some examples:</p> <ul> <li>Stream classes</li> <li>Database connections/commands</li> <li>Controls</li> </ul> <p>There's no exhaustive list of classes that implement <code>IDisposable</code>, as that list would be fairly large and filled with classes that you'll likely never encounter. Think about what the class <em>does</em>; does it open some sort of connection or file that needs to be closed? In general, <em>does it acquire some kind of resource that needs to be released</em>? If so, it probably implements it. At a basic level, if the compiler allows you to enclose it in <code>using</code>, then it implements <code>IDisposable</code>.</p> <p>As to the consequences of <em>not</em> calling <code>Dispose</code>, don't consider it. <strong>Call Dispose</strong>. True, the defensive standard is that if your class uses unmanaged resources <em>directly</em>, then you should define a finalizer that will call dispose in the event that your object is collected and someone has failed to call it, but that should not be a design choice. Ever, as far as I'm aware.</p>

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