AddOrUpdate Method (TKey, Func(TKey, TValue), Func(TKey, TValue, TValue))
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ConcurrentDictionary<TKey, TValue>.AddOrUpdate Method (TKey, Func<TKey, TValue>, Func<TKey, TValue, TValue>)

.NET Framework (current version)

Uses the specified functions to add a key/value pair to the ConcurrentDictionary<TKey, TValue> if the key does not already exist, or to update a key/value pair in the ConcurrentDictionary<TKey, TValue> if the key already exists.

Namespace:   System.Collections.Concurrent
Assembly:  mscorlib (in mscorlib.dll)

public TValue AddOrUpdate(
	TKey key,
	Func<TKey, TValue> addValueFactory,
	Func<TKey, TValue, TValue> updateValueFactory


Type: TKey

The key to be added or whose value should be updated

Type: System.Func<TKey, TValue>

The function used to generate a value for an absent key

Type: System.Func<TKey, TValue, TValue>

The function used to generate a new value for an existing key based on the key's existing value

Return Value

Type: TValue

The new value for the key. This will be either be the result of addValueFactory (if the key was absent) or the result of updateValueFactory (if the key was present).

Exception Condition

key, addValueFactory, or updateValueFactory is null.


The dictionary already contains the maximum number of elements (MaxValue).

If you call AddOrUpdate simultaneously on different threads, addValueFactory may be called multiple times, but its key/value pair might not be added to the dictionary for every call.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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