/// <summary>
/// Returns an enumerator that iterates through the collection.
/// </summary>
/// <returns>
/// A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.
/// </returns>
public IEnumerator <KeyValuePair <TKey, TValue> > GetEnumerator()
{
// Consider: we could get the enumeration of key ranges, sort them and union overlapping ranges.
// Enumerating the data as several different ranges would be more efficient when the expression
// specifies an OR and the ranges are highly disjoint.
KeyRange <TKey> range = KeyValueExpressionEvaluator <TKey, TValue> .GetKeyRange(this.expression);
this.dictionary.TraceWhere(range, this.isReversed);
if (this.isReversed)
{
return(new PersistentDictionaryReverseEnumerator <TKey, TValue, KeyValuePair <TKey, TValue> >(
this.dictionary, range, c => c.RetrieveCurrent(), this.predicate));
}
return(new PersistentDictionaryEnumerator <TKey, TValue, KeyValuePair <TKey, TValue> >(
this.dictionary, range, c => c.RetrieveCurrent(), this.predicate));
}
/// <summary>
/// Optimize a where statement which uses this dictionary.
/// </summary>
/// <param name="expression">
/// The predicate determining which items should be enumerated.
/// </param>
/// <returns>
/// An enumerator matching only the records matched by the predicate.
/// </returns>
public PersistentDictionaryLinqKeyValueEnumerable <TKey, TValue> Where(
Expression <Predicate <KeyValuePair <TKey, TValue> > > expression)
{
if (null == expression)
{
throw new ArgumentNullException("expression");
}
Predicate <KeyValuePair <TKey, TValue> > predicate =
KeyValueExpressionEvaluator <TKey, TValue> .KeyRangeIsExact(expression) ? x => true : expression.Compile();
return(new PersistentDictionaryLinqKeyValueEnumerable <TKey, TValue>(
this,
expression,
predicate,
false));
}
