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

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
Assemblies:   System.Collections.Concurrent (in System.Collections.Concurrent.dll)
  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).


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.

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Windows Phone 8.1, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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