彭泽0902 通过本文主要向大家介绍了c#dictionary用法,c#dictionary,c#遍历dictionary,c#中dictionary的用法,c#中dictionary等相关知识,希望对您有所帮助,也希望大家支持linkedu.com www.linkedu.com
在上面介绍过栈（Stack）的存储结构，接下来介绍另一种存储结构字典（Dictionary）。 字典（Dictionary）里面的每一个元素都是一个键值对(由二个元素组成：键和值) 键必须是唯一的,而值不需要唯一的,键和值都可以是任何类型。字典(Dictionary)是常用于查找和排序的列表。
接下来看一下Dictionary的部分方法和类的底层实现代码：
1.Add：将指定的键和值添加到字典中。
public void Add(TKey key, TValue value) {
Insert(key, value, true);
}
private void Insert(TKey key, TValue value, bool add) {
if( key == null ) {
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
}
if (buckets == null) Initialize(0);
int hashCode = comparer.GetHashCode(key) & 0x7FFFFFFF;
int targetBucket = hashCode % buckets.Length;
#if FEATURE_RANDOMIZED_STRING_HASHING
int collisionCount = 0;
#endif
for (int i = buckets[targetBucket]; i >= 0; i = entries[i].next) {
if (entries[i].hashCode == hashCode && comparer.Equals(entries[i].key, key)) {
if (add) {
ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_AddingDuplicate);
}
entries[i].value = value;
version++;
return;
}
#if FEATURE_RANDOMIZED_STRING_HASHING
collisionCount++;
#endif
}
int index;
if (freeCount > 0) {
index = freeList;
freeList = entries[index].next;
freeCount--;
}
else {
if (count == entries.Length)
{
Resize();
targetBucket = hashCode % buckets.Length;
}
index = count;
count++;
}
entries[index].hashCode = hashCode;
entries[index].next = buckets[targetBucket];
entries[index].key = key;
entries[index].value = value;
buckets[targetBucket] = index;
version++;
#if FEATURE_RANDOMIZED_STRING_HASHING
if(collisionCount > HashHelpers.HashCollisionThreshold && HashHelpers.IsWellKnownEqualityComparer(comparer))
{
comparer = (IEqualityComparer<TKey>) HashHelpers.GetRandomizedEqualityComparer(comparer);
Resize(entries.Length, true);
}
#endif
}
</div>
2.Clear()：从 Dictionary<TKey, TValue> 中移除所有的键和值。
public void Clear() {
if (count > 0) {
for (int i = 0; i < buckets.Length; i++) buckets[i] = -1;
Array.Clear(entries, 0, count);
freeList = -1;
count = 0;
freeCount = 0;
version++;
}
}
</div>
3.Remove()：从 Dictionary<TKey, TValue> 中移除所指定的键的值。
public bool Remove(TKey key) {
if(key == null) {
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
}
if (buckets != null) {
int hashCode = comparer.GetHashCode(key) & 0x7FFFFFFF;
int bucket = hashCode % buckets.Length;
int last = -1;
for (int i = buckets[bucket]; i >= 0; last = i, i = entries[i].next) {
if (entries[i].hashCode == hashCode && comparer.Equals(entries[i].key, key)) {
if (last < 0) {
buckets[bucket] = entries[i].next;
}
else {
entries[last].next = entries[i].next;
}
entries[i].hashCode = -1;
entries[i].next = freeList;
entries[i].key = default(TKey);
entries[i].value = default(TValue);
freeList = i;
freeCount++;
version++;
return true;
}
}
}
return false;
}
</div>
4.GetEnumerator()：返回循环访问 Dictionary<TKey, TValue> 的枚举器。
public Enumerator GetEnumerator() {
return new Enumerator(this, Enumerator.KeyValuePair);
}
[Serializable]
public struct Enumerator: IEnumerator<KeyValuePair<TKey,TValue>>,
IDictionaryEnumerator
{
private Dictionary<TKey,TValue> dictionary;
private int version;
private int index;
private KeyValuePair<TKey,TValue> current;
private int getEnumeratorRetType; // What should Enumerator.Current return?
internal const int DictEntry = 1;
internal const int KeyValuePair = 2;
internal Enumerator(Dictionary<TKey,TValue> dictionary, int getEnumeratorRetType) {
this.dictionary = dictionary;
version = dictionary.version;
index = 0;
this.getEnumeratorRetType = getEnumeratorRetType;
current = new KeyValuePair<TKey, TValue>();
}
public bool MoveNext() {
if (version != dictionary.version) {
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
}
// Use unsigned comparison since we set index to dictionary.count+1 when the enumeration ends.
// dictionary.count+1 could be negative if dictionary.count is Int32.MaxValue
while ((uint)index < (uint)dictionary.count) {
if (dictionary.entries[index].hashCode >= 0) {
current = new KeyValuePair<TKey, TValue>(dictionary.entries[index].key, dictionary.entries[index].value);
index++;
return true;
}
index++;
}
index = dictionary.count + 1;
current = new KeyValuePair<TKey, TValue>();
return false;
}
public KeyValuePair<TKey,TValue> Current {
get { return current; }
}
public void Dispose() {
}
object IEnumerator.Current {
get {
if( index == 0 || (index == dictionary.count + 1)) {
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen);
}
if (getEnumeratorRetType == DictEntry) {
return new System.Collections.DictionaryEntry(current.Key, current.Value);
} else {
return new KeyValuePair<TKey, TValue>(current.Key, current.Value);
}
}
}
void IEnumerator.Reset() {
if (version != dictionary.version) {
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumFailedVersion);
}
index = 0;
current = new KeyValuePair<TKey, TValue>();
}
DictionaryEntry IDictionaryEnumerator.Entry {
get {
if( index == 0 || (index == dictionary.count + 1)) {
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen);
}
return new DictionaryEntry(current.Key, current.Value);
}
}
object IDictionaryEnumerator.Key {
get {
if( index == 0 || (index == dictionary.count + 1)) {
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen);
}
return current.Key;
}
}
object IDictionaryEnumerator.Value {
get {
if( index == 0 || (index == dictionary.count + 1)) {
ThrowHelper.ThrowInvalidOperationException(ExceptionResource.InvalidOperation_EnumOpCantHappen);
}
return current.Value;
}
}
}
</div>
上面主要是对字典(Dictionary)的一些常用方法进行一个简单的说明。接下来主要阐述如何创建安全的字典(Dictionary)存储结构。有关线程安全的部分，在这里就不再赘