C# 0 The Complete Reference

AddMemoryPressure( )

 and 

RemoveMemoryPressure( )

. These are used to 

indicate that a large amount of unmanaged memory has been allocated or released by the 

program. They are important because the memory management system has no oversight 

on unmanaged memory. If a program allocates a large amount of unmanaged memory, then 

performance might be affected because the system has no way of knowing that free memory 

has been reduced. By calling 

AddMemoryPressure( )

 when allocating large amounts of 

unmanaged memory, you let the CLR know that memory has been reduced. By calling 

RemoveMemoryPressure( )

, you let the CLR know the memory has been freed. Remember: 

RemoveMemoryPressure( )

 must be called only to indicate that memory reported by a call 

to

AddMemoryPressure( )

 has been released.

Method

Meaning

public static void

    AddMemor yPressure(long 

size

)

Indicates that 

size

 number of bytes of unmanaged 

memor y have been allocated. 

public static void Collect( )

Initiates garbage collection.

public static void Collect(int 

maxGen

)

Initiates garbage collection for memor y with generation 

numbers of 0 through 

maxGen.

public static void Collect(int 

maxGen

,

                  GCCollectionMode 

GCMode

)

Initiates garbage collection for memor y with generation 

numbers of 0 through 

maxGen

 as specified by 

GCMode

.

public static int CollectionCount(int 

gen

)

Returns the number of garbage collections that have 

taken place for memor y having the generation number 

specified by 

gen.

public static int GetGeneration(object 

o

)

Returns the generation number for the memor y referred 

to by 

o.

public static int

    GetGeneration(WeakReference 

o

)

Returns the generation number for the memor y 

referred to by the weak reference specified by 

o.

 A 

weak reference does not prevent the object from being 

garbage-collected.

public static long

    GetTotalMemor y(bool 

collect

)

Returns the total number of bytes currently allocated. If 

collect

 is true, garbage collection occurs first. 

public static void KeepAlive(object 

o

)

Creates a reference to 

o,

 thus preventing it from being 

garbage collected. This reference ends when 

KeepAlive( )

executes.

public static void

    RemoveMemor yPressure(long 

size

)

Indicates that 

size

 number of bytes of unmanaged 

memor y have been released. 

public static void

    ReRegisterForFinalize(object 

o

)

Causes the finalizer (i.e., the destructor) for 

o

 to be called. 

This method undoes the effects of 

SuppressFinalize( )

.

public static void

    SuppressFinalize(object 

o

)

Prevents the finalizer (i.e., the destructor) for 

o

 from 

being called. 

public static void

    WaitForPendingFinalizers( )

Halts execution of the invoking thread until all pending 

finalizers (i.e., destructors) have been called.

T

ABLE

 21-15 

Methods Defi ned by 

GC

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