1+ using System ;
2+ using System . Collections ;
3+ using System . Collections . Generic ;
4+
5+ namespace CodingMilitia . MoarCollections . Dictionaries
6+ {
7+ /// <summary>
8+ /// <para>
9+ /// Acts as a wrapper over a <see cref="Dictionary{TKey, TValue}"/> with the ability of returning a default value (static or using a <see cref="Func{TKey, TValue}"/>)
10+ /// when the requested key is not present.
11+ /// </para>
12+ /// <para>
13+ /// Most of the times, using <see cref="IDictionary{TKey, TValue}.TryGetValue(TKey, out TValue)"/> on a regular Dictionary will be good enough,
14+ /// this should only be useful when you just want to index and forget.
15+ /// </para>
16+ /// <para>The <see cref="Func{TKey, TValue}"/> can be also useful in cases we want to throw a specific exception when the key is not found.</para>
17+ /// </summary>
18+ /// <typeparam name="TKey"></typeparam>
19+ /// <typeparam name="TValue"></typeparam>
20+ public class DictionaryWithDefaultValue < TKey , TValue > : IDictionary < TKey , TValue >
21+ {
22+ private readonly Dictionary < TKey , TValue > _backingDictionary ;
23+ private readonly TValue _defaultValue ;
24+ private readonly Func < TKey , TValue > _defaultValueFunc ;
25+
26+ public DictionaryWithDefaultValue ( TValue defaultValue )
27+ {
28+ _backingDictionary = new Dictionary < TKey , TValue > ( ) ;
29+ _defaultValue = defaultValue ;
30+ _defaultValueFunc = null ;
31+ }
32+
33+ public DictionaryWithDefaultValue ( IDictionary < TKey , TValue > sourceDictionary , TValue defaultValue )
34+ {
35+ _backingDictionary = sourceDictionary != null ? new Dictionary < TKey , TValue > ( sourceDictionary ) : throw new ArgumentNullException ( nameof ( sourceDictionary ) ) ;
36+ _defaultValue = defaultValue ;
37+ _defaultValueFunc = null ;
38+ }
39+
40+ public DictionaryWithDefaultValue ( Func < TKey , TValue > defaultValueFunc )
41+ {
42+ _backingDictionary = new Dictionary < TKey , TValue > ( ) ;
43+ _defaultValue = default ( TValue ) ;
44+ _defaultValueFunc = defaultValueFunc ?? throw new ArgumentNullException ( nameof ( defaultValueFunc ) ) ;
45+ }
46+
47+ public DictionaryWithDefaultValue ( IDictionary < TKey , TValue > sourceDictionary , Func < TKey , TValue > defaultValueFunc )
48+ {
49+ _backingDictionary = sourceDictionary != null ? new Dictionary < TKey , TValue > ( sourceDictionary ) : throw new ArgumentNullException ( nameof ( sourceDictionary ) ) ;
50+ _defaultValue = default ( TValue ) ;
51+ _defaultValueFunc = defaultValueFunc ?? throw new ArgumentNullException ( nameof ( defaultValueFunc ) ) ;
52+ }
53+
54+ public TValue this [ TKey key ]
55+ {
56+ get => _backingDictionary . TryGetValue ( key , out var value ) ? value : _defaultValueFunc != null ? _defaultValueFunc ( key ) : _defaultValue ;
57+ set => _backingDictionary [ key ] = value ;
58+ }
59+
60+ public ICollection < TKey > Keys => _backingDictionary . Keys ;
61+
62+ public ICollection < TValue > Values => _backingDictionary . Values ;
63+
64+ public int Count => _backingDictionary . Count ;
65+
66+ public bool IsReadOnly => ( ( IDictionary < TKey , TValue > ) _backingDictionary ) . IsReadOnly ;
67+
68+ public void Add ( TKey key , TValue value ) => _backingDictionary . Add ( key , value ) ;
69+
70+ public void Add ( KeyValuePair < TKey , TValue > item ) => ( ( IDictionary < TKey , TValue > ) _backingDictionary ) . Add ( item ) ;
71+
72+ public void Clear ( ) => _backingDictionary . Clear ( ) ;
73+
74+ public bool Contains ( KeyValuePair < TKey , TValue > item ) => ( ( IDictionary < TKey , TValue > ) _backingDictionary ) . Contains ( item ) ;
75+
76+ public bool ContainsKey ( TKey key ) => _backingDictionary . ContainsKey ( key ) ;
77+
78+ public void CopyTo ( KeyValuePair < TKey , TValue > [ ] array , int arrayIndex ) => ( ( IDictionary < TKey , TValue > ) _backingDictionary ) . CopyTo ( array , arrayIndex ) ;
79+
80+ public IEnumerator < KeyValuePair < TKey , TValue > > GetEnumerator ( ) => _backingDictionary . GetEnumerator ( ) ;
81+
82+ public bool Remove ( TKey key ) => _backingDictionary . Remove ( key ) ;
83+
84+ public bool Remove ( KeyValuePair < TKey , TValue > item ) => ( ( IDictionary < TKey , TValue > ) _backingDictionary ) . Remove ( item ) ;
85+
86+ public bool TryGetValue ( TKey key , out TValue value ) => _backingDictionary . TryGetValue ( key , out value ) ;
87+
88+ IEnumerator IEnumerable . GetEnumerator ( ) => GetEnumerator ( ) ;
89+ }
90+ }
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