Hastable in C#: Using the same key multiple times

Question

I fetch multiple records with the same id and I want to store them in a Hashtable in C#. I'm using the id as the key in the Hashtable, and the value is the object itself. It throws an exception because the same key is added again. Is there a way to fix this problem?

This is my code:

Hashtable localItemsIndex = new Hashtable();            
foreach (TzThing thing in localThingz)
         localItemsIndex.Add(thing.Id, thing);

Thanks in advance jennie

Do you *have* to use the old non-generic collections, or are you happy for us to propose solutions based on .NET 2 and higher? What about LINQ? — Jon Skeet, Mar 08 '11 at 11:29

Stecya · Accepted Answer · 2011-03-15T06:45:31.200

7

Maybe you should use Dictionary<Id,List<TzThing>> to store multiple values for one key

public void Add(YourIdType key,TzThing thing )
{
   if(dictionary.ContainsKey(key))
   {
      dictionary[key].Add(thing);
   }
   else
   {
      dictionary.Add(key,new List<TzThing> {thing});
   }
}

edited Mar 15 '11 at 06:45

answered Mar 08 '11 at 11:29

Stecya

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Can u please brief me how to store in dictionary for same key – user642378 Mar 15 '11 at 05:51

score 1 · Answer 2 · answered Mar 08 '11 at 11:31

The hashtable key must be unique: you can't add the same key twice into it. You may use List or HashSet where T is the key-value pair of your class (or use the .net KeyValuePair class) or the Dictionary class where V the list or set but you'll still need to manage the duplicate key insertion manually.

score 0 · Answer 3 · answered Mar 08 '11 at 11:29

0

If you have many things to go with the same key, put your things in a List.

answered Mar 08 '11 at 11:29

d-live

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score 0 · Answer 4 · answered Mar 15 '11 at 07:29

0

You cannot use HashTable for this. It only accepts unique keys. Otherwise you need to use List<T> with KeyValuePair<key,value> class.

answered Mar 15 '11 at 07:29

Anuraj

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Hastable in C#: Using the same key multiple times

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