CODEWITHSUNDEEP
c#.netcollections
user2837961
user2837961

Reputation: 1555

Unique pair collection

I want to store two strings in a collection but the combination should be unique eg

'1','2'
'2','1'
'1','2' -> not allowed
'2','3'

Which collection should I use if I want both strings to be keys?

Upvotes: 2

Views: 6403

Answers (4)

Patrick Hofman
Patrick Hofman

Reputation: 156948

Use a HashSet<CustomObject>, with a custom IEqualityComparer. The comparer makes sure that no entries are allowed with duplicate values. I just wrote a sample implementation, adapt it to your convenience.

HashSet<CustomObject> x = new HashSet<CustomObject>(new XE());

public class CustomObjectEqualityComparer : IEqualityComparer<CustomObject>
{
    public bool Equals(CustomObject x, CustomObject y)
    {
        return x.Var1 == y.Var1 && x.Var2 == y.Var2;
    }

    public int GetHashCode(string obj)
    {
        //
    }
}

public class CustomObject
{
    public string Var1 { get; set; }
    public string Var2 { get; set; }
}

Upvotes: 3

Eamonn McEvoy
Eamonn McEvoy

Reputation: 8986

Use a HashSet of KeyValuePair<String, String>.

For example:

HashSet<KeyValuePair<String, String>> set = new HashSet<KeyValuePair<string, string>>();
set.Add(new KeyValuePair<string, string>("1", "2"));
set.Add(new KeyValuePair<string, string>("1", "2"));

This will produce only one entry in the set.

For reference:

KeyValuePair Class

HashSet Class

Upvotes: 4

Midhun Mundayadan
Midhun Mundayadan

Reputation: 3182

No duplicates returned

   static NameValueCollection GetCollection()
    {
    NameValueCollection collection = new NameValueCollection();
    collection.Add("Sam", "Dot Net Perls");
    collection.Add("Bill", "Microsoft");
    collection.Add("Bill", "White House");
    collection.Add("Sam", "IBM");
    return collection;
    }

    static void Main()
    {
    NameValueCollection collection = GetCollection();
    foreach (string key in collection.AllKeys) // <-- No duplicates returned.
    {
        Console.WriteLine(key);
    }

duplicates return

public class ListWithDuplicates : List<KeyValuePair<string, string>>
{
    public void Add(string key, string value)
    {
        var element = new KeyValuePair<string, string>(key, value);
        this.Add(element);
    }
}

var list = new ListWithDuplicates();
list.Add("rr", "11");
list.Add("rr", "22");
list.Add("rr", "33");

foreach(var item in list)
{
    string x = string.format("{0}={1}, ", item.Key, item.Value);
}

Outputs rr=11, rr=22, rr=33.

Upvotes: 0

Felipe Oriani
Felipe Oriani

Reputation: 38598

Try using a custom type and a hashSet collection. For sample:

public class Item : IEqualityComparer<Item>
{
    public string Value1 { get; set; }
    public string Value2 { get; set; }

    public bool Equals(Item x, Item y)
    {
        return x.Valie1 == y.Value1 && x.Value2 != y.Value2;
    }

    public int GetHashCode(string obj)
    {
        // implement
    }
}

Use a hashSet

HashSet<Item> set = new HashSet<Item>();
set.Add(new Item() { Value1 = "1", Value2 = "1" });

Upvotes: 1

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