Print out contents of a hashtable

7 Sep 2006 11:21 AM

Water Cooler v2

I can't believe I've stumbled on a simple problem such as this. After
all these years, that too.

Anyway, it goes that I just realized that I could not iterate through
my hashtable and print out its contents. On further probing, I realized
that the hashtable didn't implenent IList, which really has the
this[int] indexer. And so I couldnt do this:

for (int i = 0; i < _myHashTable.Count; i++)
Console.WriteLine(_myHashTable[i].ToString());

I had to know the key to index the hashtable elements. I could
enumerate through it by getting its enumerator
(IEnumerable.GetEnumerator) and then calling Next() and Current on its
IEnumerator but even then, I'd have to know the keys.

I took the hashtable in the first place because of its Contains method.
It can easily reference its elements and check for the existence of a
key, in constant time whereas list takes linear time.

Now, I am stuck. All I need to do is print out the contents of the
hashtable. The other option I can consider is to take a Dictionary or a
NameValueCollection or to take an ArrayList and extend it to have a
Contains look up method.

7 Sep 2006 11:32 AM

Water Cooler v2

People, never mind, I am using a System.Collections.SortedList. It's
got what I need.

bool Contains(key);
object GetKey(int);

And I don't mind if the items are all sorted.

7 Sep 2006 11:41 AM

Kerry Moorman

Water Cooler v2,

Think of the hashtable as a collection of DictionaryEntry objects, with your
custom object stored in the DictionaryEntry's Value property.

Use a For Each loop to iterate through the hashtable and cast your object
from DictionaryEntry.Value:

     For Each de As DictionaryEntry in myHashTable
         myObject = DirectCast (de.Value, myClass)
     Next

Kerry Moorman

Show quote

"Water Cooler v2" wrote:

> I can't believe I've stumbled on a simple problem such as this. After
> all these years, that too.
>
> Anyway, it goes that I just realized that I could not iterate through
> my hashtable and print out its contents. On further probing, I realized
> that the hashtable didn't implenent IList, which really has the
> this[int] indexer. And so I couldnt do this:
>
> for (int i = 0; i < _myHashTable.Count; i++)
> Console.WriteLine(_myHashTable[i].ToString());
>
> I had to know the key to index the hashtable elements. I could
> enumerate through it by getting its enumerator
> (IEnumerable.GetEnumerator) and then calling Next() and Current on its
> IEnumerator but even then, I'd have to know the keys.
>
> I took the hashtable in the first place because of its Contains method.
> It can easily reference its elements and check for the existence of a
> key, in constant time whereas list takes linear time.
>
> Now, I am stuck. All I need to do is print out the contents of the
> hashtable. The other option I can consider is to take a Dictionary or a
> NameValueCollection or to take an ArrayList and extend it to have a
> Contains look up method.
>
>

7 Sep 2006 11:45 AM

Truong Hong Thi

To iterate:
foreach (DictionaryEntry entry in t)
{
Console.WriteLine("{0}: {1}", entry.Key, entry.Value);
}

If you want to check if the hash table contains a key/value, try using
ContainKey (same as Contains, but method name makes it clearer) and
ContainsValue methods.

Water Cooler v2 wrote:
Show quote

> I can't believe I've stumbled on a simple problem such as this. After
> all these years, that too.
>
> Anyway, it goes that I just realized that I could not iterate through
> my hashtable and print out its contents. On further probing, I realized
> that the hashtable didn't implenent IList, which really has the
> this[int] indexer. And so I couldnt do this:
>
> for (int i = 0; i < _myHashTable.Count; i++)
> Console.WriteLine(_myHashTable[i].ToString());
>
> I had to know the key to index the hashtable elements. I could
> enumerate through it by getting its enumerator
> (IEnumerable.GetEnumerator) and then calling Next() and Current on its
> IEnumerator but even then, I'd have to know the keys.
>
> I took the hashtable in the first place because of its Contains method.
> It can easily reference its elements and check for the existence of a
> key, in constant time whereas list takes linear time.
>
> Now, I am stuck. All I need to do is print out the contents of the
> hashtable. The other option I can consider is to take a Dictionary or a
> NameValueCollection or to take an ArrayList and extend it to have a
> Contains look up method.

7 Sep 2006 12:40 PM

Water Cooler v2

Oh yeah! Thanks, Kerry and Truong. I was wondering how I could cast the
"object" inside the hashtable into an object that looked like a
dictionaryentry. Only, I didn't see the obvious.