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

Adds a key/value pair to the ConcurrentDictionary(TKey, TValue) if the key does not already exist, or updates a key/value pair in the ConcurrentDictionary(TKey, TValue) by using the specified function if the key already exists.

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

member AddOrUpdate : 
        key:'TKey * 
        addValue:'TValue * 
        updateValueFactory:Func<'TKey, 'TValue, 'TValue> -> 'TValue 


Type: TKey

The key to be added or whose value should be updated

Type: TValue

The value to be added 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 addValue (if the key was absent) or the result of updateValueFactory (if the key was present).


key or updateValueFactory is a null reference (Nothing in Visual Basic).


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

The following code example shows how to initialize an ConcurrentDictionary(TKey, TValue) and how to use the AddOrUpdate method to add an additional item to the collection, and update the existing items.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1
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