KGy SOFT

LockingDictionaryTKey, TValue Class

KGy SOFT Core Libraries Help
Provides a simple wrapper for an IDictionaryTKey, TValue where all members are thread-safe. This only means that the inner state of the wrapped dictionary remains always consistent and not that all of the multi-threading concerns can be ignored.
See the Remarks section for details and some examples.
Inheritance Hierarchy

SystemObject
  KGySoft.CollectionsLockingCollectionKeyValuePairTKey, TValue
    KGySoft.CollectionsLockingDictionaryTKey, TValue

Namespace:  KGySoft.Collections
Assembly:  KGySoft.CoreLibraries (in KGySoft.CoreLibraries.dll) Version: 5.0.0-rc.1
Syntax

[SerializableAttribute]
public class LockingDictionary<TKey, TValue> : LockingCollection<KeyValuePair<TKey, TValue>>, 
	IDictionary<TKey, TValue>, ICollection<KeyValuePair<TKey, TValue>>, 
	IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable

Type Parameters

TKey
The type of the keys in the dictionary.
TValue
The type of the values in the dictionary.

The LockingDictionaryTKey, TValue type exposes the following members.

Constructors

  NameDescription
Public methodLockingDictionaryTKey, TValue
Initializes a new instance of the LockingDictionaryTKey, TValue class with a DictionaryTKey, TValue inside.
Public methodLockingDictionaryTKey, TValue(IDictionaryTKey, TValue)
Initializes a new instance of the LockingDictionaryTKey, TValue class.
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Properties

  NameDescription
Public propertyCount (Inherited from LockingCollectionT.)
Public propertyIsReadOnly (Inherited from LockingCollectionT.)
Public propertyItem
Gets or sets the element with the specified key.
Public propertyKeys
Gets an ICollectionT containing the keys of the LockingDictionaryTKey, TValue.
Public propertyValues
Gets an ICollectionT containing the values of the LockingDictionaryTKey, TValue.
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Methods

  NameDescription
Public methodAdd(T) (Inherited from LockingCollectionT.)
Public methodAdd(TKey, TValue)
Adds an element with the provided key and value to the LockingDictionaryTKey, TValue.
Public methodClear (Inherited from LockingCollectionT.)
Public methodContains (Inherited from LockingCollectionT.)
Public methodContainsKey
Determines whether the LockingDictionaryTKey, TValue contains an element with the specified key.
Public methodCopyTo (Inherited from LockingCollectionT.)
Public methodEquals
Determines whether the specified object is equal to the current object.
(Inherited from Object.)
Protected methodFinalize
Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.
(Inherited from Object.)
Public methodGetEnumerator
Returns an enumerator that iterates through the collection.
(Inherited from LockingCollectionT.)
Public methodGetHashCode
Serves as the default hash function.
(Inherited from Object.)
Public methodGetType
Gets the Type of the current instance.
(Inherited from Object.)
Public methodLock
Locks the access of the underlying collection from other threads until Unlock is called as many times as this method was called. Needed to be called if multiple calls to the wrapped collection have to be combined without releasing the lock between each calls.
See the Remarks section of the LockingCollectionT class for details and some examples.
(Inherited from LockingCollectionT.)
Protected methodMemberwiseClone
Creates a shallow copy of the current Object.
(Inherited from Object.)
Public methodRemove(T) (Inherited from LockingCollectionT.)
Public methodRemove(TKey)
Removes the element with the specified key from the LockingDictionaryTKey, TValue.
Public methodToString
Returns a string that represents the current object.
(Inherited from Object.)
Public methodTryGetValue
Gets the value associated with the specified key.
Public methodUnlock
When called as many times as Lock was called previously, then unlocks the access of the underlying collection so other threads also can access it.
(Inherited from LockingCollectionT.)
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Extension Methods

  NameDescription
Public Extension MethodAddRangeKeyValuePairTKey, TValue (Defined by CollectionExtensions.)
Public Extension MethodAsThreadSafeKeyValuePairTKey, TValue (Defined by CollectionExtensions.)
Public Extension MethodConvert(Type, CultureInfo)Overloaded.
Converts an Object specified in the obj parameter to the desired targetType.
See the Examples section of the generic ConvertTTarget(Object, CultureInfo) overload for an example.
(Defined by ObjectExtensions.)
Public Extension MethodCode exampleConvertTTarget(CultureInfo)Overloaded.
Converts an Object specified in the obj parameter to the desired TTarget.
(Defined by ObjectExtensions.)
Public Extension MethodForEachKeyValuePairTKey, TValue
Similarly to the List<T>.ForEach method, processes an action on each element of an enumerable collection.
(Defined by EnumerableExtensions.)
Public Extension MethodGetRandomElementKeyValuePairTKey, TValue(Boolean)Overloaded.
Gets a random element from the enumerable source using a new Random instance.
(Defined by EnumerableExtensions.)
Public Extension MethodGetRandomElementKeyValuePairTKey, TValue(Random, Boolean)Overloaded.
Gets a random element from the enumerable source using a specified Random instance.
(Defined by EnumerableExtensions.)
Public Extension MethodIn (Defined by ObjectExtensions.)
Public Extension MethodIndexOf(FuncObject, Boolean)Overloaded.
Searches for an element in the source enumeration where the specified predicate returns .
(Defined by EnumerableExtensions.)
Public Extension MethodIndexOf(Object)Overloaded.
Searches for an element in the source enumeration.
(Defined by EnumerableExtensions.)
Public Extension MethodIndexOfKeyValuePairTKey, TValue(FuncKeyValuePairTKey, TValue, Boolean)Overloaded.
Searches for an element in the source enumeration where the specified predicate returns .
(Defined by EnumerableExtensions.)
Public Extension MethodIndexOfKeyValuePairTKey, TValue(KeyValuePairTKey, TValue)Overloaded.
Searches for an element in the source enumeration.
(Defined by EnumerableExtensions.)
Public Extension MethodIsNullOrEmptyOverloaded.
Determines whether the specified source is  or empty (has no elements).
(Defined by EnumerableExtensions.)
Public Extension MethodIsNullOrEmptyKeyValuePairTKey, TValueOverloaded.
Determines whether the specified source is  or empty (has no elements).
(Defined by EnumerableExtensions.)
Public Extension MethodShuffleKeyValuePairTKey, TValueOverloaded.
Shuffles an enumerable source (randomizes its elements) using a new Random instance.
(Defined by EnumerableExtensions.)
Public Extension MethodShuffleKeyValuePairTKey, TValue(Int32)Overloaded.
Shuffles an enumerable source (randomizes its elements) using the provided seed with a new Random instance.
(Defined by EnumerableExtensions.)
Public Extension MethodShuffleKeyValuePairTKey, TValue(Random)Overloaded.
Shuffles an enumerable source (randomizes its elements) using a specified Random instance.
(Defined by EnumerableExtensions.)
Public Extension MethodToCircularListKeyValuePairTKey, TValue (Defined by EnumerableExtensions.)
Public Extension MethodTryAdd(Object, Boolean, Boolean)Overloaded.
Tries to add the specified item to the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryAddKeyValuePairTKey, TValue(KeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to add the specified item to the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryAddRange(IEnumerable, Boolean, Boolean)Overloaded.
Tries to add the specified collection to the target collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryAddRangeKeyValuePairTKey, TValue(IEnumerableKeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to add the specified collection to the target collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryClear(Boolean, Boolean)Overloaded.
Tries to remove all elements from the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryClearKeyValuePairTKey, TValue(Boolean, Boolean)Overloaded.
Tries to remove all elements from the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryConvert(Type, Object)Overloaded.
Tries to convert an Object specified in the obj parameter to the desired targetType.
(Defined by ObjectExtensions.)
Public Extension MethodTryConvert(Type, CultureInfo, Object)Overloaded.
Tries to convert an Object specified in the obj parameter to the desired targetType.
(Defined by ObjectExtensions.)
Public Extension MethodTryConvertTTarget(TTarget)Overloaded.
Tries to convert an Object specified in the obj parameter to the desired TTarget.
See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example.
(Defined by ObjectExtensions.)
Public Extension MethodTryConvertTTarget(CultureInfo, TTarget)Overloaded.
Tries to convert an Object specified in the obj parameter to the desired TTarget.
See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example.
(Defined by ObjectExtensions.)
Public Extension MethodTryGetElementAt(Int32, Object, Boolean, Boolean)Overloaded.
Tries to get an item at the specified index in the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryGetElementAtKeyValuePairTKey, TValue(Int32, KeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to get an item at the specified index in the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryInsert(Int32, Object, Boolean, Boolean)Overloaded.
Tries to insert the specified item at the specified index to the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryInsertKeyValuePairTKey, TValue(Int32, KeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to insert the specified item at the specified index to the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryInsertRange(Int32, IEnumerable, Boolean, Boolean)Overloaded.
Tries to insert the specified collection into the target collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryInsertRangeKeyValuePairTKey, TValue(Int32, IEnumerableKeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to insert the specified collection into the target collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryRemove(Object, Boolean, Boolean)Overloaded.
Tries to remove the specified item from to the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryRemoveKeyValuePairTKey, TValue(KeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to remove the specified item from to the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryRemoveAt(Int32, Boolean, Boolean)Overloaded.
Tries to remove an item at the specified index from the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryRemoveAtKeyValuePairTKey, TValue(Int32, Boolean, Boolean)Overloaded.
Tries to remove an item at the specified index from the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTryRemoveRange(Int32, Int32, Boolean, Boolean)Overloaded.
Tries to remove count amount of items from the specified collection at the specified index.
(Defined by EnumerableExtensions.)
Public Extension MethodTryRemoveRangeKeyValuePairTKey, TValue(Int32, Int32, Boolean, Boolean)Overloaded.
Tries to remove count amount of items from the specified collection at the specified index.
(Defined by EnumerableExtensions.)
Public Extension MethodTryReplaceRange(Int32, Int32, IEnumerable, Boolean, Boolean)Overloaded.
Tries to remove count amount of items from the target at the specified index, and to insert the specified collection at the same position. The number of elements in collection can be different from the amount of removed items.
(Defined by EnumerableExtensions.)
Public Extension MethodTryReplaceRangeKeyValuePairTKey, TValue(Int32, Int32, IEnumerableKeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to remove count amount of items from the target at the specified index, and to insert the specified collection at the same position. The number of elements in collection can be different from the amount of removed items.
(Defined by EnumerableExtensions.)
Public Extension MethodTrySetElementAt(Int32, Object, Boolean, Boolean)Overloaded.
Tries to set the specified item at the specified index in the collection.
(Defined by EnumerableExtensions.)
Public Extension MethodTrySetElementAtKeyValuePairTKey, TValue(Int32, KeyValuePairTKey, TValue, Boolean, Boolean)Overloaded.
Tries to set the specified item at the specified index in the collection.
(Defined by EnumerableExtensions.)
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Remarks

Type safety means that all members of the underlying collection are accessed in a lock, which only provides that the collection remains consistent as long as it is accessed only by the members of this class. This does not solve every issue of multi-threading automatically. Consider the following example:

C#
var asThreadSafe = new LockingDictionary<MyKey, MyValue>(myDictionary);

// Though both calls use locks it still can happen that two threads try to add the same key twice this way
// because the lock is released between the two calls:
if (!asThreadSafe.ContainsKey(myKey))
    asThreadSafe.Add(myKey, myValue);

For the situations above a lock can be requested also explicitly by the Lock method, which can be released by the Unlock method. To release an explicitly requested lock the Unlock method must be called the same times as the Lock method. The fixed version of the example above:

C#
var asThreadSafe = new LockingDictionary<MyClass>(myDictionary);

// This works well because the lock is not released between the two calls:
asThreadSafe.Lock();
try
{
    if (!asThreadSafe.ContainsKey(myKey))
        asThreadSafe.Add(myKey, myValue);
}
finally
{
    asThreadSafe.Unlock();
}

To avoid confusion, the non-generic IDictionary interface is not implemented by the LockingDictionaryTKey, TValue class because it uses a different aspect of synchronization.

The GetEnumerator method and Keys and Values properties create a snapshot of the underlying collections so obtaining these members have an O(n) cost on this class.

Note Note
Starting with .NET 4 a sort of concurrent collections appeared. While they provide good scalability for multiple concurrent readers by using separate locks for entries or for a set of entries, in many situations they perform worse than a simple locking collection, especially if the collection to lock uses a fast accessible storage (eg. an array) internally. It also may worth to mention that some members (such as the Count property) are surprisingly expensive operations on most concurrent collections as they traverse the inner storage and in the meantime they lock all entries while counting the elements. So it always depends on the concrete scenario whether a simple locking collection or a concurrent collection is more beneficial to use.

Thread Safety

Instance members of this type are safe for multi-threaded operations.
See Also

Reference