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

.NET Framework (current version)

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Adds a key/value pair to the ConcurrentDictionary<TKey, TValue> by using the specified function, if the key does not already exist.

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

public TValue GetOrAdd(
	TKey key,
	Func<TKey, TValue> valueFactory


Type: TKey

The key of the element to add.

Type: System.Func<TKey, TValue>

The function used to generate a value for the key

Return Value

Type: TValue

The value for the key. This will be either the existing value for the key if the key is already in the dictionary, or the new value for the key as returned by valueFactory if the key was not in the dictionary.

Exception Condition

key or valueFactory is null.


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

If you call GetOrAdd 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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