Thread Safety of static Array used as lookup table

18 Jan 2006 2:51 PM

Mark M

Hi all,

Is the follow construct thread safe to access via indexer?

public static readonly string [] GradeLookupTable = new string[]
{
"*","PK","K","1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","HS","UG"
};

Usage:

string grade = GradeLookupTable[12];

Thanks for your help!

18 Jan 2006 3:53 PM

NuTcAsE

> Is the follow construct thread safe to access via indexer?
Yes

But you should know that setting the field as readonly doesnt mean that
the values of the array cannot be altered. The following code will
change the value of the element at index 2:

GrageLookupTable[2] = "Test";

To make it truly readonly, make the field a property and return a clone
of the array so that no one can change the original values of the
array:

public static Grades {
get {return GradeLookupTable.Clone() as string[];}
}

- NuTcAsE

18 Jan 2006 5:45 PM

Jon Skeet [C# MVP]

NuTcAsE <rao.rit***@gmail.com> wrote:
Show quote

> > Is the follow construct thread safe to access via indexer?
> Yes
>
> But you should know that setting the field as readonly doesnt mean that
> the values of the array cannot be altered. The following code will
> change the value of the element at index 2:
>
> GrageLookupTable[2] = "Test";
>
> To make it truly readonly, make the field a property and return a clone
> of the array so that no one can change the original values of the
> array:
>
> public static Grades {
> get {return GradeLookupTable.Clone() as string[];}
> }

Or preferrably provide a property which provides a read-only view on
the array - you don't really want to create a new copy of the array
every time you access the property.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
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