Define the Set Class(C#)

using System.Collections;//
namespace ClassSetPractise
{
public class CSet
{
//the two most important properties of sets are that
//the members of a set are unordered and no member
//can occur in a set more than once
//we only need one data member and one structors members for our CSet
private Hashtable data;
public CSet()
{
data = new Hashtable();
}

public void Add(Object item)
{
if (!(data.ContainsValue(item)))
{
data.Add(Hash(item),item);
}
}
private string Hash(Object item)
{
char[] chars;
int hashValue = 0;
string s = item.ToString();
chars = s.ToCharArray();
for (int i = 0; i <= chars.GetUpperBound(0); i++)
{
hashValue += (int)chars[i];
}
return hashValue.ToString();
}

public void Remove(Object item)
{
data.Remove(Hash(item));
}

public int Size()
{
return data.Count;
}

public CSet Union(CSet aSet)
{
CSet tempSet = new CSet();
foreach (Object hashObject in data.Keys)
{
tempSet.Add(this.data[hashObject]);
}
foreach (Object hashObject in aSet.data.Keys)
{
if (!(this.data.ContainsKey(hashObject)))
{
tempSet.Add(aSet.data[hashObject]);
}
}

return tempSet;
}

public CSet Intersection(CSet aSet)
{
CSet tempSet = new CSet();
foreach (Object hashObject in data.Keys)
{
if (aSet.data.Contains(hashObject))
{
tempSet.Add(aSet.data[hashObject]);//
}
}
return tempSet;
}

public bool Subset(CSet aSet)
{
//if (this.Size > aSet.Size)
//{
// return false;
//}
//else
//{
foreach (Object key in this.data.Keys)
{
if (!(aSet.data.Contains(key)))
{
return false;
}
}
//}
return true;
}

public CSet Different(CSet aSet)
{
CSet tempSet = new CSet();
foreach (Object hashObject in data.Keys)
{
if (!(aSet.data.Contains(hashObject)))
{
tempSet.Add(data[hashObject]);
}
}
return tempSet;
}

public override string ToString()
{
string s = "";
foreach (Object key in data.Keys)
{
s += data[key]+" ";
}
return s;
}
}
class Program
{
static void Main(string[] args)
{
CSet setA = new CSet();
CSet setB = new CSet();

setA.Add("milk");
setA.Add("eggs");
setA.Add("bacon");
setA.Add("cereal");

setB.Add("bacon");
setB.Add("eggs");
setB.Add("bread");

CSet setC = new CSet();
setC = setA.Union(setB);
Console.WriteLine();
Console.WriteLine("A: "+setA.ToString());
Console.WriteLine("B: "+setB.ToString());
Console.WriteLine("A union B: "+setC.ToString());
setC = setA.Intersection(setB);
Console.WriteLine("A intersect B: "+setC.ToString());
setC = setA.Different(setB);
Console.WriteLine("B diff A: "+setC.ToString());
if (setB.Subset(setA))
{
Console.WriteLine("B is a subset of A");
}
else
{
Console.WriteLine("B is not a subset of A");
}
}
}
}