Something to note about Hashtables

I was actually using the Dictionary class, but the Keys of a Dictionary is a Hashtable, so it has the same issue.
When you try and add two value types of the same type to a Hashtable, it blows up, saying "Item has already been added".

System.Collections.Hashtable ht = new System.Collections.Hashtable();

ht.Add(new Guid(), "hello");
ht.Add(new Guid(), "hello");


One thought on “Something to note about Hashtables

  1. Actually this makes sense:   Guid is a value type with a default value of Guid.Empty, so in your sample you’re adding the same value for the key twice.i.e what you did was the same as ht.Add("A", "hello");
    ht.Add("A", "hello");or the same asht.Add(666, "hello");
    ht.Add(666, "hello");

    If you were to go:Hashtable ht = new HashTable();ht.Add(Guid.NewGuid(), "hello");ht.Add(Guid.NewGuid(), "hello");that would work.

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