Find a value from a hashtable

Question

If I were having a Generic list I would have done some thing like this

myListOfObject.FindAll(x=>(x.IsRequired==false));

What if I need to do similar stuff in Hashtable? Copying to temporary hashtable and looping and comparing would be that last thing I would try :-(

Solution

Firstly, use System.Collections.Generic.Dictionary<TKey, TValue> for better strong-type support as opposed to Hashtable.

If you need to just find one key or one value, use the methods ContainsKey(object key) or ContainsValue(object value), both of which are found on the Hashtable type.

Or you can go further and use linq extensions on the Hashtable parts:

Hashtable t = new Hashtable();
t.Add("Key", "Adam");

// Get the key/value entries.
var itemEntry = t.OfType<DictionaryEntry>().Where(de => (de.Value as string) == "Adam");

// Get just the values.
var items = t.Values.OfType<string>().Where(s => s == "Adam");

// Get just the keys.
var itemKey = t.Keys.OfType<string>().Where(k => k == "Key");