LockingDictionaryTKey, TValue Class

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.

Definition

Namespace: KGySoft.Collections
Assembly: KGySoft.CoreLibraries (in KGySoft.CoreLibraries.dll) Version: 8.2.0
C#
[SerializableAttribute]
public class LockingDictionary<TKey, TValue> : LockingCollection<KeyValuePair<TKey, TValue>>, 
	IDictionary<TKey, TValue>, ICollection<KeyValuePair<TKey, TValue>>, 
	IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable, IReadOnlyDictionary<TKey, TValue>, 
	IReadOnlyCollection<KeyValuePair<TKey, TValue>>
Inheritance
Object    LockingCollectionKeyValuePairTKey, TValue    LockingDictionaryTKey, TValue
Implements
ICollectionKeyValuePairTKey, TValue, IDictionaryTKey, TValue, IEnumerableKeyValuePairTKey, TValue, IReadOnlyCollectionKeyValuePairTKey, TValue, IReadOnlyDictionaryTKey, TValue, IEnumerable

Type Parameters

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

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<MyKey, MyValue>(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

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.

  Tip

Constructors

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

Properties

Count Gets the number of elements contained in the LockingCollectionT.
(Inherited from LockingCollectionT)
IsReadOnly Gets a value indicating whether the LockingCollectionT is read-only.
(Inherited from LockingCollectionT)
Item Gets or sets the element with the specified key.
Keys Gets an ICollectionT containing the keys of the LockingDictionaryTKey, TValue.
Values Gets an ICollectionT containing the values of the LockingDictionaryTKey, TValue.

Methods

Add(T) Adds an item to the LockingCollectionT.
(Inherited from LockingCollectionT)
Add(TKey, TValue) Adds an element with the provided key and value to the LockingDictionaryTKey, TValue.
Clear Removes all items from the LockingCollectionT.
(Inherited from LockingCollectionT)
Contains Determines whether the LockingCollectionT contains a specific value.
(Inherited from LockingCollectionT)
ContainsKey Determines whether the LockingDictionaryTKey, TValue contains an element with the specified key.
CopyTo Copies the elements of the LockingCollectionT to an Array, starting at a particular arrayIndex.
(Inherited from LockingCollectionT)
GetEnumerator Returns an enumerator that iterates through the collection.
(Inherited from LockingCollectionT)
Lock 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)
Remove(T) Removes the first occurrence of a specific object from the LockingCollectionT.
(Inherited from LockingCollectionT)
Remove(TKey) Removes the element with the specified key from the LockingDictionaryTKey, TValue.
TryGetValue Gets the value associated with the specified key.
Unlock 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)

Extension Methods

AddRangeKeyValuePairTKey, TValue Adds a collection to the target ICollectionT.
(Defined by CollectionExtensions)
AsThreadSafeKeyValuePairTKey, TValue Returns a LockingCollectionT, which provides a thread-safe wrapper for the specified collection. This only means that if the members are accessed through the returned LockingCollectionT, then the inner state of the wrapped collection remains always consistent and not that all of the multi-threading concerns can be ignored.
See the Remarks section of the LockingCollectionT class for details and some examples.
(Defined by CollectionExtensions)
Convert 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)
ConvertTTarget Converts an Object specified in the obj parameter to the desired TTarget.
(Defined by ObjectExtensions)
ForEachKeyValuePairTKey, TValue Similarly to the List<T>.ForEach method, processes an action on each element of an enumerable collection.
(Defined by EnumerableExtensions)
GetRandomElementKeyValuePairTKey, TValue Gets a random element from the enumerable source using a new FastRandom instance.
(Defined by EnumerableExtensions)
GetRandomElementKeyValuePairTKey, TValue Gets a random element from the enumerable source using a specified Random instance.
(Defined by EnumerableExtensions)
In Gets whether item is among the elements of set.
See the Examples section of the generic InT(T, T) overload for an example.
(Defined by ObjectExtensions)
IndexOf Searches for an element in the source enumeration where the specified predicate returns .
(Defined by EnumerableExtensions)
IndexOf Searches for an element in the source enumeration.
(Defined by EnumerableExtensions)
IndexOfKeyValuePairTKey, TValue Searches for an element in the source enumeration where the specified predicate returns .
(Defined by EnumerableExtensions)
IndexOfKeyValuePairTKey, TValue Searches for an element in the source enumeration.
(Defined by EnumerableExtensions)
IsNullOrEmpty Determines whether the specified source is or empty (has no elements).
(Defined by EnumerableExtensions)
IsNullOrEmptyKeyValuePairTKey, TValue Determines whether the specified source is or empty (has no elements).
(Defined by EnumerableExtensions)
JoinKeyValuePairTKey, TValue Concatenates the items of the source collection into a new string instance using the specified separator between the items.
(Defined by EnumerableExtensions)
JoinKeyValuePairTKey, TValue Concatenates the items of the source collection into a new string instance using the specified separator between the items.
(Defined by EnumerableExtensions)
ShuffleKeyValuePairTKey, TValue Shuffles an enumerable source (randomizes its elements) using a new FastRandom instance.
(Defined by EnumerableExtensions)
ShuffleKeyValuePairTKey, TValue Shuffles an enumerable source (randomizes its elements) using the provided seed with a new FastRandom instance.
(Defined by EnumerableExtensions)
ShuffleKeyValuePairTKey, TValue Shuffles an enumerable source (randomizes its elements) using the provided seed with a new FastRandom instance.
(Defined by EnumerableExtensions)
ShuffleKeyValuePairTKey, TValue Shuffles an enumerable source (randomizes its elements) using a specified Random instance.
(Defined by EnumerableExtensions)
ToCircularListKeyValuePairTKey, TValue Creates a CircularListT from an IEnumerableT.
(Defined by EnumerableExtensions)
ToStringKeyedDictionaryKeyValuePairTKey, TValue Creates a StringKeyedDictionaryTValue from an IEnumerableT instance using the specified keySelector delegate and a comparer.
(Defined by EnumerableExtensions)
ToStringKeyedDictionaryKeyValuePairTKey, TValue, TValue Creates a StringKeyedDictionaryTValue from an IEnumerableT instance using the specified key and value selector delegates and a comparer.
(Defined by EnumerableExtensions)
TryAdd Tries to add the specified item to the collection.
(Defined by EnumerableExtensions)
TryAddKeyValuePairTKey, TValue Tries to add the specified item to the collection.
(Defined by EnumerableExtensions)
TryAddRange Tries to add the specified collection to the target collection.
(Defined by EnumerableExtensions)
TryAddRangeKeyValuePairTKey, TValue Tries to add the specified collection to the target collection.
(Defined by EnumerableExtensions)
TryClear Tries to remove all elements from the collection.
(Defined by EnumerableExtensions)
TryClearKeyValuePairTKey, TValue Tries to remove all elements from the collection.
(Defined by EnumerableExtensions)
TryConvert Tries to convert an Object specified in the obj parameter to the desired targetType.
See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example.
(Defined by ObjectExtensions)
TryConvert Tries to convert an Object specified in the obj parameter to the desired targetType.
See the Examples section of the ConvertTTarget(Object, CultureInfo) method for a related example.
(Defined by ObjectExtensions)
TryConvertTTarget 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)
TryConvertTTarget 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)
TryGetCount Tries to get the number of elements in the source enumeration without enumerating it.
(Defined by EnumerableExtensions)
TryGetCountKeyValuePairTKey, TValue Tries to get the number of elements in the source enumeration without enumerating it.
(Defined by EnumerableExtensions)
TryGetElementAt Tries to get an item at the specified index in the collection.
(Defined by EnumerableExtensions)
TryGetElementAtKeyValuePairTKey, TValue Tries to get an item at the specified index in the collection.
(Defined by EnumerableExtensions)
TryInsert Tries to insert the specified item at the specified index to the collection.
(Defined by EnumerableExtensions)
TryInsertKeyValuePairTKey, TValue Tries to insert the specified item at the specified index to the collection.
(Defined by EnumerableExtensions)
TryInsertRange Tries to insert the specified collection into the target collection.
(Defined by EnumerableExtensions)
TryInsertRangeKeyValuePairTKey, TValue Tries to insert the specified collection into the target collection.
(Defined by EnumerableExtensions)
TryRemove Tries to remove the specified item from to the collection.
(Defined by EnumerableExtensions)
TryRemoveKeyValuePairTKey, TValue Tries to remove the specified item from to the collection.
(Defined by EnumerableExtensions)
TryRemoveAt Tries to remove an item at the specified index from the collection.
(Defined by EnumerableExtensions)
TryRemoveAtKeyValuePairTKey, TValue Tries to remove an item at the specified index from the collection.
(Defined by EnumerableExtensions)
TryRemoveRange Tries to remove count amount of items from the specified collection at the specified index.
(Defined by EnumerableExtensions)
TryRemoveRangeKeyValuePairTKey, TValue Tries to remove count amount of items from the specified collection at the specified index.
(Defined by EnumerableExtensions)
TryReplaceRange 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)
TryReplaceRangeKeyValuePairTKey, TValue 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)
TrySetElementAt Tries to set the specified item at the specified index in the collection.
(Defined by EnumerableExtensions)
TrySetElementAtKeyValuePairTKey, TValue Tries to set the specified item at the specified index in the collection.
(Defined by EnumerableExtensions)

Thread Safety

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

See Also