Collection order

[Mike]

If I create a collection and add members using the Add() method, is is
guarenteed that the members will be returned in the same order that they
were added, if:

i) I enumerate using a foreach loop?
ii) I index from 0 to Count-1 using a for loop?

Cheers,

Mike

 

[Mark Colburn]

-----Original Message-----
If I create a collection and add members using the Add() method, is is
guarenteed that the members will be returned in the same order that they
were added, if:

i) I enumerate using a foreach loop?
ii) I index from 0 to Count-1 using a for loop?

No, it's not. Some collections are ordered, and others
are not: it depends on the semantics of the collection.
Some collections, such as ArrayList will return the
collection in order. Others such as Hashtable will return
items according to their hash value; Dictionary will sort
by the key value.

-mark

 

[Mike]

If I create a collection and add members using the Add()

method, is is

No, it's not. Some collections are ordered, and others
are not: it depends on the semantics of the collection.
Some collections, such as ArrayList will return the
collection in order. Others such as Hashtable will return
items according to their hash value; Dictionary will sort
by the key value.

Thanks for your help, I understand now.

With regards to ordering, what will the behaviour be of a class that
inherits from CollectionBase?

Mike

 

[Anders Borum]

Hello!

With regards to ordering, what will the behaviour be of a class that
inherits from CollectionBase?

It is ordered!

 

[Mike]

With regards to ordering, what will the behaviour be of a class that

It is ordered!

Thanks... how can you tell this?

Mike

 

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

Hello!


It is ordered!

I really don;t think that, CollectionBase use an ArrayList instance for
storing the values , if ArrayList is not sorted ( as Colburn's said ) then
the CollectionBase is by default not sorted.

You can sort it , though , just including a Sort method that return a new
collection sorted. This is very easy to do

Cheers,

 

[Jon Skeet [C# MVP]]

<"Ignacio Machin \( .NET/ C# MVP \)" <ignacio.machin AT

I really don;t think that, CollectionBase use an ArrayList instance for
storing the values , if ArrayList is not sorted ( as Colburn's said ) then
the CollectionBase is by default not sorted.

You can sort it , though , just including a Sort method that return a new
collection sorted. This is very easy to do

There's a difference between "sorted" and "ordered". A CollectionBase
*is* ordered, but *isn't* sorted.

 

[Mike]

You can sort it , though , just including a Sort method that return a
new

There's a difference between "sorted" and "ordered". A CollectionBase
*is* ordered, but *isn't* sorted.

So if CollectionBase is ordered, then all collections are ordered?

Mike

 

[Jon Skeet [C# MVP]]

So if CollectionBase is ordered, then all collections are ordered?

No, because not all collections derive from CollectionBase.