Hello.

Sometimes I encounter the following problem:

foreach( element of some collection)
{
delete this element;
}

of course, the runtime would not allow to modify
the collection whilst executing loop through
its elements.

I often happen to write solutoin to this problem
by myself, but i am curious if there is some
design pattern how to handle such a situation
(the need to delete element of collection being ierated
through)

Thaks for answer
Michal Januszczyk

One trick is to use "for(){}" backward, insteadof "foreach(){}":

for (int i=myCollection.Count-1; i>=0; i--)
{
myCollection.RemoveAt(i)
//Or your own Delete(i)/Remove(i) method, because if you remove item
//from a collection backward, remaining item's index will not change
}

"Michal Januszczyk" <(E-Mail Removed)> wrote in message
news:036301c3c8ee$a22bb190$(E-Mail Removed)...
> Hello.
>
> Sometimes I encounter the following problem:
>
> foreach( element of some collection)
> {
> delete this element;
> }
>
> of course, the runtime would not allow to modify
> the collection whilst executing loop through
> its elements.
>
> I often happen to write solutoin to this problem
> by myself, but i am curious if there is some
> design pattern how to handle such a situation
> (the need to delete element of collection being ierated
> through)
>
> Thaks for answer
> Michal Januszczyk

Hi,

I also faced this problem and incorporated the following
solution for the same.

// Create a Hashtable and clone the existing HashTable
(accessible through the InnerHashtable property of the
types derived from the DictionaryBase class).

System.Collections.Hashtable LocalHashTable =
(System.Collections.Hashtable)this.InnerHashtable.Clone();

// Create an IEnumerator type instance, so as to traverse
the collection.

System.Collections.IEnumerator KeysEnumerator =
LocalHashTable.GetEnumerator();

// Finally traverse the collection
while (KeysEnumerator.MoveNext())
{
// Now you can manipulate the collection.
this.Dictionary.Remove(OldCellKey);
}



Regards,
Puneet Taneja


>-----Original Message-----
>One trick is to use "for(){}" backward,
insteadof "foreach(){}":
>
>for (int i=myCollection.Count-1; i>=0; i--)
>{
> myCollection.RemoveAt(i)
> //Or your own Delete(i)/Remove(i) method, because if
you remove item
> //from a collection backward, remaining item's index
will not change
>}
>
>"Michal Januszczyk"
<(E-Mail Removed)> wrote in message
>news:036301c3c8ee$a22bb190$(E-Mail Removed)...
>> Hello.
>>
>> Sometimes I encounter the following problem:
>>
>> foreach( element of some collection)
>> {
>> delete this element;
>> }
>>
>> of course, the runtime would not allow to modify
>> the collection whilst executing loop through
>> its elements.
>>
>> I often happen to write solutoin to this problem
>> by myself, but i am curious if there is some
>> design pattern how to handle such a situation
>> (the need to delete element of collection being ierated
>> through)
>>
>> Thaks for answer
>> Michal Januszczyk
>
>
>.
>

If you create the iterator against a clone of the collection, you can delete from the original collection while continuing to iterate the clone

"
Private ie as IEnumerator = MyList.Clone.GetEnumerator()
"


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