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I N D E X E R S, O P E R ATO R S, A N D   P O I N T E R S

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8849CH12.qxd  9/26/07  11:31 AM  Page 409

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Thus, if you create a Point type (now redesigned as a class) and want to interact with its mem-

bers, you must write the following code (or receive a compiler error):

unsafe public static void UseAndPinPoint()

{

PointRef pt = new PointRef ();

pt.x = 5;

pt.y = 6;

// pin pt in place so it will not

// be moved or GC-ed.

fixed (int* p = &pt.x)

{

// Use int* variable here!

}

// pt is now unpinned, and ready to be GC-ed.

Console.WriteLine ("Point is: {0}", pt);

}

In a nutshell, the fixed keyword allows you to build a statement that locks a reference variable

in memory, such that its address remains constant for the duration of the statement. To be sure, any

time you interact with a reference type from within the context of unsafe code, pinning the refer-

ence is a must.