C# 0 The Complete Reference

prop

, and a property called 

MyProp

 that manages access to 

prop

. As explained, a property 

by itself does not define a storage location. Instead, most properties simply manage access 

to a field. Furthermore, because 

prop

 is private, it can be accessed 

only

 through 

MyProp

.

The property 

MyProp

 is specified as 

public

 so it can be accessed by code outside of its 

class. This makes sense because it provides access to 

prop

, which is private. The 

get

 accessor 

simply returns the value of 

prop

. The 

set

 accessor sets the value of 

prop

 if and only if that 

value is positive. Thus, the 

MyProp

 property controls what values 

prop

 can have. This is 

the essence of why properties are important.

The type of property defined by 

MyProp

 is called a read-write property because it allows 

its underlying field to be read and written. It is possible, however, to create read-only and 

write-only properties. To create a read-only property, define only a 

get

 accessor. To define a 

write-only property, define only a 

set

 accessor.

You can use a property to further improve the fail-soft array class. As you know, all 

arrays have a 

Length

 property associated with them. Up to now, the 

FailSoftArray

 class 

simply used a public integer field called 

Length

 for this purpose. This is not good practice, 

though, because it allows 

Length

 to be set to some value other than the length of the fail-

soft array. (For example, a malicious programmer could intentionally corrupt its value.) We 

can remedy this situation by transforming 

Length

 into a read-only property, as shown in 

the following version of 

FailSoftArray

:

// Add Length property to FailSoftArray.

using System;

class FailSoftArray {

  int[] a; // reference to underlying array

  int len; // length of array -- underlies Length property

  public bool ErrFlag; // indicates outcome of last operation

  // Construct array given its size.

  public FailSoftArray(int size) {

    a = new int[size];

    len = size;

  }

  // Read-only Length property.

  public int Length {

    get {

      return len;

    }

  }

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