Removing from a dictionary all the elements where the keys satisfy a set of conditions is something I needed to do more than once so I implemented it as an extension method to the IDictionary<TKey, TValue> interface.
Here’s the code:
public static class DictionaryExtensions
{
/// <summary>
/// Removes all the elements where the key
match the conditions defined by the specified predicate.
/// </summary>
/// <typeparam name="TKey">
/// The type of the dictionary key.
/// </typeparam>
/// <typeparam name="TValue">
/// The type of the dictionary value.
/// </typeparam>
/// <param name="dictionary">
/// A dictionary from which to remove the matched keys.
/// </param>
/// <param name="match">
/// The <see cref="Predicate{T}"/> delegate that defines the conditions of the keys to remove.
/// </param>
/// <exception cref="ArgumentNullException">
/// dictionary is null
/// <br />-or-<br />
///
match is null.
/// </exception>
/// <returns>
/// The number of elements removed from the <see cref="IDictionary{TKey, TValue}"/>.
/// </returns>
public static int RemoveAll<TKey, TValue>(
this IDictionary<TKey, TValue> dictionary,
Predicate<TKey> match)
{
if (dictionary == null)
throw new ArgumentNullException("dictionary");
if (match == null)
throw new ArgumentNullException("match");
var keysToRemove = dictionary.Keys.Where(k => match(k)).ToList();
if (keysToRemove.Count == 0)
return 0;
foreach (var key in keysToRemove)
{
dictionary.Remove(key);
}
return keysToRemove.Count;
}
}
