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<overview>

<p>Microsoft defines two broad categories for source code. Managed code compiles into bytecode and is then executed by a virtual

machine. Unmanaged code is compiled directly into machine code. All C# code is managed but it is possible to call external unmanaged

code. This metric counts the number of <code>extern</code> methods in each class that are implemented by unmanaged code. Managed code has many advantages

over unmanaged code such as built in memory management performed by the virtual machine and the ability to run compiled programs

on a wider variety of architectures.</p>

</overview>

<recommendation>

<p>Consider whether the unmanaged methods could be replaced by managed code instead.</p>

</recommendation>

<example>

<p>This example shows a function that displays a message box when clicked. It is implemented with

unmanaged code from the <code>User32.dll</code> library.</p>

<sample src="TUnmanagedCode.cs" />

</example>

<section title="Fixing by Using Managed Code">

<p>This example uses managed code to perform the same function.</p>

<sample src="TUnmanagedCodeFix.cs" />

</section>

<references>

<li>MSDN, C# Reference. <a href="http://msdn.microsoft.com/en-us/library/e59b22c5(v=vs.80).aspx">extern</a>.</li>

<li>Wikipedia. <a href="http://en.wikipedia.org/wiki/Managed_code">Managed code</a>.</li>

</references>

</qhelp>