Class HashMap<TKey, TValue>

A C# emulation of the Java Hashmap

A is a close equivalent to the Java Hashmap. One difference java implementation of the class is that the Hashmap supports both null keys and values, where the C# Dictionary only supports null values not keys. Also, V Get(TKey) method in Java returns null if the key doesn't exist, instead of throwing an exception. In .NET, using TryGetValue(TKey, out TValue) will provide similar behavior as V Get(TKey) This class is slower than using a , because of extra checks that have to be done on each access, to check for null.

Consider also implementing IDictionary, IEnumerable, and ICollection like does, so HashMap can be used in substituted in place for the same interfaces it implements.

Inheritance

System.Object

HashMap<TKey, TValue>

IdentityHashMap<TKey, TValue>

LinkedHashMap<TKey, TValue>

Namespace: Lucene.Net.Support

Assembly: Lucene.Net.dll

Syntax

public class HashMap<TKey, TValue> : IDictionary<TKey, TValue>

Type Parameters

Name	Description
TKey	The type of keys in the dictionary
TValue	The type of values in the dictionary

Remarks

Unordered Dictionaries

- use when order is not important and all keys are non-null.
HashMap<TKey, TValue> - use when order is not important and support for a null key is required.

Ordered Dictionaries

LinkedHashMap<TKey, TValue> - use when you need to preserve entry insertion order. Keys are nullable.
- use when you need natural sort order. Null keys are not supported.
TreeDictionary<TKey, TValue> - use when you need natural sort order. Keys are nullable.
LurchTable<TKey, TValue> - use when you need to sort by most recent access or most recent update. Works well for LRU caching.

Constructors

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HashMap()

Declaration

public HashMap()

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HashMap(IEnumerable<KeyValuePair<TKey, TValue>>)

Declaration

public HashMap(IEnumerable<KeyValuePair<TKey, TValue>> other)

Parameters

Type	Name	Description
IEnumerable<KeyValuePair<TKey, TValue>>	other

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HashMap(IEqualityComparer<TKey>)

Declaration

public HashMap(IEqualityComparer<TKey> comparer)

Parameters

Type	Name	Description
IEqualityComparer<TKey>	comparer

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HashMap(Int32)

Declaration

public HashMap(int initialCapacity)

Parameters

Type	Name	Description
System.Int32	initialCapacity

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HashMap(Int32, IEqualityComparer<TKey>)

Declaration

public HashMap(int initialCapacity, IEqualityComparer<TKey> comparer)

Parameters

Type	Name	Description
System.Int32	initialCapacity
IEqualityComparer<TKey>	comparer

Properties

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Count

Declaration

public virtual int Count { get; }

Property Value

Type	Description
System.Int32

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IsReadOnly

Declaration

public virtual bool IsReadOnly { get; }

Property Value

Type	Description
System.Boolean

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Item[TKey]

Declaration

public virtual TValue this[TKey key] { get; set; }

Parameters

Type	Name	Description
TKey	key

Property Value

Type	Description
TValue

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Keys

Declaration

public virtual ICollection<TKey> Keys { get; }

Property Value

Type	Description
ICollection<TKey>

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Values

Declaration

public virtual ICollection<TValue> Values { get; }

Property Value

Type	Description
ICollection<TValue>

Methods

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Add(TKey, TValue)

Declaration

public virtual void Add(TKey key, TValue value)

Parameters

Type	Name	Description
TKey	key
TValue	value

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Add(KeyValuePair<TKey, TValue>)

Declaration

public virtual void Add(KeyValuePair<TKey, TValue> item)

Parameters

Type	Name	Description
KeyValuePair<TKey, TValue>	item

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AddIfAbsent(TKey, TValue)

Declaration

public TValue AddIfAbsent(TKey key, TValue value)

Parameters

Type	Name	Description
TKey	key
TValue	value

Returns

Type	Description
TValue

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Clear()

Declaration

public virtual void Clear()

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Contains(KeyValuePair<TKey, TValue>)

Declaration

public virtual bool Contains(KeyValuePair<TKey, TValue> item)

Parameters

Type	Name	Description
KeyValuePair<TKey, TValue>	item

Returns

Type	Description
System.Boolean

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ContainsKey(TKey)

Declaration

public virtual bool ContainsKey(TKey key)

Parameters

Type	Name	Description
TKey	key

Returns

Type	Description
System.Boolean

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ContainsValue(TValue)

Declaration

public bool ContainsValue(TValue value)

Parameters

Type	Name	Description
TValue	value

Returns

Type	Description
System.Boolean

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CopyTo(KeyValuePair<TKey, TValue>[], Int32)

Declaration

public virtual void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)

Parameters

Type	Name	Description
KeyValuePair<TKey, TValue>[]	array
System.Int32	arrayIndex

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Equals(Object)

Declaration

public override bool Equals(object obj)

Parameters

Type	Name	Description
System.Object	obj

Returns

Type	Description
System.Boolean

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GetEnumerator()

Declaration

public virtual IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()

Returns

Type	Description
IEnumerator<KeyValuePair<TKey, TValue>>

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GetHashCode()

Declaration

public override int GetHashCode()

Returns

Type	Description
System.Int32

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Remove(TKey)

Declaration

public virtual bool Remove(TKey key)

Parameters

Type	Name	Description
TKey	key

Returns

Type	Description
System.Boolean

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Remove(KeyValuePair<TKey, TValue>)

Declaration

public virtual bool Remove(KeyValuePair<TKey, TValue> item)

Parameters

Type	Name	Description
KeyValuePair<TKey, TValue>	item

Returns

Type	Description
System.Boolean

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ToString()

Declaration

public override string ToString()

Returns

Type	Description
System.String

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TryGetValue(TKey, out TValue)

Declaration

public virtual bool TryGetValue(TKey key, out TValue value)

Parameters

Type	Name	Description
TKey	key
TValue	value

Returns

Type	Description
System.Boolean