Count unique values in ArrayList C#

[GTXY20]

Hi all,

I have an ArrayList1 of multiple values. Here is an exaple of the a potential ArrayList1:

a,a,b,,c,a,b,c,c,c,a,b

Does anyone have any suggestion whereby I could output the count for wach unique item:

a=4
b=3
c=4

I have done this in python with a defaultdict(int) and was wondering if there was a quick way in C# to do this other than creating another ArrayList2 containing a unique set of the items from all od the items in ArrayList1 and then iterating through ArrayList1 counting the values for i where i is drevied from ArrayList2.

Any guidance or a starting point is much appreciated.

G.

[GTXY20]

The list of values were kept in a dictionary so I have a dictionary with a key value pair where the value is a list of items.

data = new Dictionary<string, List<string>>
 

I ended up placing the items from the value list of the dictionary into two additonal lists a list of distinct values (itemsunique) and then used a foreach loop on a complete list of all the values for all keys in the (allitems):

List<string> allitems = new List<string>();
List<string> itemsunique = new List<string>();
 
foreach (KeyValuePair<string, List<string>> s in data)
{
foreach (string h in s.Value)
{
allitems.Add(h);
allitems.Sort();
 
if (!itemsunique.Contains(h))
{
itemsunique.Add(h);
itemsunique.Sort();
}
 
}
}
 
 
int count = 0;
foreach (string y in itemsunique)
{
count = allitems.count(n=> n == y);
Console.Writeline("{0}={1} ", y, count);
}
 

However I will have several lists that I will need to apply this to and afraid that this will be memory intensive if I have to do with each list considering some lists will be quite large with over 100k items.

Any suggestions or comments are appreciated.

Thanks.

g.

[GTXY20]

Further I was able to do the same using a hashtable:

 
Hashtable items = new Hashtable();
if (!items.Contains(itemfromlist))
       items.Add(itemfromlist, 1);
else
       items[itemfromlist] = (int) items[itemfromlist]+1