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Source Code

The CustomConversions project is located under the Chapter 12 subdirectory.

Working with Pointer Types

In Chapter 4, you learned that the .NET platform defines two major categories of data: value types

and reference types. Truth be told, however, there is a third category: 

pointer types. To work with

pointer types, we are provided with specific operators and keywords that allow us to bypass the

CLR’s memory management scheme and take matters into our own hands (see Table 12-3).

Table 12-3.

Pointer-Centric C# Operators and Keywords

Operator/Keyword

Meaning in Life

*

This operator is used to create a pointer variable (i.e., a variable that

represents a direct location in memory). As in C(++), this same operator is

used for pointer indirection.

&

This operator is used to obtain the address of a variable in memory.

->

This operator is used to access fields of a type that is represented by a pointer

(the unsafe version of the C# dot operator).

[]

The [] operator (in an unsafe context) allows you to index the slot pointed to

by a pointer variable (recall the interplay between a pointer variable and the

[] operator in C(++)!).

++, --

In an unsafe context, the increment and decrement operators can be applied

to pointer types.

+, -

In an unsafe context, the addition and subtraction operators can be applied

to pointer types.

==, !=, <, >, <=, =>

In an unsafe context, the comparison and equality operators can be applied

to pointer types.

stackalloc

In an unsafe context, the stackalloc keyword can be used to allocate C#

arrays directly on the stack.

fixed

In an unsafe context, the fixed keyword can be used to temporarily fix a

variable so that its address may be found. 

Now, before we dig into the details, let me point out the fact that you will 

seldom if ever need to

make use of pointer types. Although C# does allow you to drop down to the level of pointer manipu-

lations, understand that the .NET runtime has absolutely no clue of your intentions. Thus, if you

mismanage a pointer, you are the one in charge of dealing with the consequences. Given these

warnings, when exactly would you need to work with pointer types? There are two common

situations:

• You are looking to optimize select parts of your application by directly manipulating mem-

ory outside the management of the CLR.

• You are calling methods of a C-based *.dll or COM server that demand pointer types as

parameters. Even in this case, you can often bypass the use of pointer types in favor of the

System.IntPtr type and members of the System.Runtime.InteropServices.Marshal type.

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