Answer Posted / sivaprasad

1)In Array We Can Add any datatype value,Every item in
arraylist is treated as object.
2)Hashtable is collection of key,value pairs
i)Key Can be any datatype
ii)Key Cannot be null refrrence
iii)but value can be null referrence

Retrieving by key in Hashtable is faster than retrieving in
Arraylist,
Example of Arraylist:
Arraylist ar = new Arraylist();
ar.add("X");
ar.add(1);
ar.add(2);
Now if we Retrieve from Arraylist like
foreach(string str in ar)
{

}
It will Compile but it will give Runtime
Error,because '1' and '2' in Arraylist are integers.

Example Hashtable:
Hashtable ht = new Hashtable();
ht.add(1,"sample");
ht.add("2","Test");
ht.add(3,4);
foreach(Dictionaryentry dr in ht.keys.values)
{
Console.Writeline(dr.keys + "=" + dr.values);
}

The Above Code wont give any runtime Error Because We
are iterating through DictionaryEntries(Hashtable
implements IDictionary) it is Collection of Key/Value Pairs

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