ConcurrentDictionary<TKey,TValue>.AddOrUpdate Method

Source:

ConcurrentDictionary.cs

Source:

ConcurrentDictionary.cs

Source:

ConcurrentDictionary.cs

public:
 TValue AddOrUpdate(TKey key, Func<TKey, TValue> ^ addValueFactory, Func<TKey, TValue, TValue> ^ updateValueFactory);

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

member this.AddOrUpdate : 'Key * Func<'Key, 'Value> * Func<'Key, 'Value, 'Value> -> 'Value

Public Function AddOrUpdate (key As TKey, addValueFactory As Func(Of TKey, TValue), updateValueFactory As Func(Of TKey, TValue, TValue)) As TValue

Parameters

Returns

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).

Exceptions

Remarks

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.

For modifications and write operations to the dictionary, ConcurrentDictionary<TKey,TValue> uses fine-grained locking to ensure thread safety (read operations on the dictionary are performed in a lock-free manner). The addValueFactory and updateValueFactory delegates may be executed multiple times to verify the value was added or updated as expected. However, they are called outside the locks to avoid the problems that can arise from executing unknown code under a lock. Therefore, AddOrUpdate is not atomic with regards to all other operations on the ConcurrentDictionary<TKey,TValue> class.

See also

• Thread-Safe Collections
• How to: Add and Remove Items from a ConcurrentDictionary

Source:

ConcurrentDictionary.cs

Source:

ConcurrentDictionary.cs

Source:

ConcurrentDictionary.cs

public:
 TValue AddOrUpdate(TKey key, TValue addValue, Func<TKey, TValue, TValue> ^ updateValueFactory);

public TValue AddOrUpdate (TKey key, TValue addValue, Func<TKey,TValue,TValue> updateValueFactory);

member this.AddOrUpdate : 'Key * 'Value * Func<'Key, 'Value, 'Value> -> 'Value

Public Function AddOrUpdate (key As TKey, addValue As TValue, updateValueFactory As Func(Of TKey, TValue, TValue)) As TValue

Parameters

Returns

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).

Exceptions

Examples

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.

using System;
using System.Collections.Concurrent;

class CD_Ctor
{
    // Demonstrates:
    //      ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity)
    //      ConcurrentDictionary<TKey, TValue>[TKey]
    static void Main()
    {
        // We know how many items we want to insert into the ConcurrentDictionary.
        // So set the initial capacity to some prime number above that, to ensure that
        // the ConcurrentDictionary does not need to be resized while initializing it.
        int HIGHNUMBER = 64;
        int initialCapacity = 101;

        // The higher the concurrencyLevel, the higher the theoretical number of operations
        // that could be performed concurrently on the ConcurrentDictionary.  However, global
        // operations like resizing the dictionary take longer as the concurrencyLevel rises.
        // For the purposes of this example, we'll compromise at numCores * 2.
        int numProcs = Environment.ProcessorCount;
        int concurrencyLevel = numProcs * 2;

        // Construct the dictionary with the desired concurrencyLevel and initialCapacity
        ConcurrentDictionary<int, int> cd = new ConcurrentDictionary<int, int>(concurrencyLevel, initialCapacity);

        // Initialize the dictionary
        for (int i = 1; i <= HIGHNUMBER; i++) cd[i] = i * i;

        Console.WriteLine("The square of 23 is {0} (should be {1})", cd[23], 23 * 23);

        // Now iterate through, adding one to the end of the list. Existing items should be updated to be divided by their
        // key  and a new item will be added that is the square of its key.
        for (int i = 1; i <= HIGHNUMBER + 1; i++)
          cd.AddOrUpdate(i, i * i, (k,v) => v / i);

        Console.WriteLine("The square root of 529 is {0} (should be {1})", cd[23], 529 / 23);
        Console.WriteLine("The square of 65 is {0} (should be {1})", cd[HIGHNUMBER + 1], ((HIGHNUMBER + 1) * (HIGHNUMBER + 1)));
    }
}

open System
open System.Collections.Concurrent

// Demonstrates:
//      ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity)
//      ConcurrentDictionary<TKey, TValue>[TKey]

// We know how many items we want to insert into the ConcurrentDictionary.
// So set the initial capacity to some prime number above that, to ensure that
// the ConcurrentDictionary does not need to be resized while initializing it.
let HIGHNUMBER = 64
let initialCapacity = 101

// The higher the concurrencyLevel, the higher the theoretical number of operations
// that could be performed concurrently on the ConcurrentDictionary.  However, global
// operations like resizing the dictionary take longer as the concurrencyLevel rises.
// For the purposes of this example, we'll compromise at numCores * 2.
let numProcs = Environment.ProcessorCount
let concurrencyLevel = numProcs * 2

// Construct the dictionary with the desired concurrencyLevel and initialCapacity
let cd = ConcurrentDictionary<int, int>(concurrencyLevel, initialCapacity)

// Initialize the dictionary
for i = 1 to HIGHNUMBER do
    cd[i] <- i * i

printfn $"The square of 23 is {cd[23]} (should be {23 * 23})"

// Now iterate through, adding one to the end of the list. Existing items should be updated to be divided by their
// key  and a new item will be added that is the square of its key.
for i = 1 to HIGHNUMBER + 1 do
    cd.AddOrUpdate(i, i * i, (fun k v -> v / i)) |> ignore

printfn $"The square root of 529 is {cd[23]} (should be {529 / 23})"
printfn $"The square of 65 is {cd[HIGHNUMBER + 1]} (should be {(HIGHNUMBER + 1) * (HIGHNUMBER + 1)})"

Imports System.Collections.Concurrent

Class CD_Ctor
    ' Demonstrates: 
    '      ConcurrentDictionary<TKey, TValue> ctor(concurrencyLevel, initialCapacity) 
    '      ConcurrentDictionary<TKey, TValue>[TKey] 
    Public Shared Sub Main()
        ' We know how many items we want to insert into the ConcurrentDictionary. 
        ' So set the initial capacity to some prime number above that, to ensure that 
        ' the ConcurrentDictionary does not need to be resized while initializing it. 
        Dim HIGHNUMBER As Integer = 64
        Dim initialCapacity As Integer = 101

        ' The higher the concurrencyLevel, the higher the theoretical number of operations 
        ' that could be performed concurrently on the ConcurrentDictionary.  However, global 
        ' operations like resizing the dictionary take longer as the concurrencyLevel rises.  
        ' For the purposes of this example, we'll compromise at numCores * 2. 
        Dim numProcs As Integer = Environment.ProcessorCount
        Dim concurrencyLevel As Integer = numProcs * 2

        ' Construct the dictionary with the desired concurrencyLevel and initialCapacity
        Dim cd As New ConcurrentDictionary(Of Integer, Integer)(concurrencyLevel, initialCapacity)

        ' Initialize the dictionary 
        For i As Integer = 1 To HIGHNUMBER
            cd(i) = i * i
        Next

        Console.WriteLine("The square of 23 is {0} (should be {1})", cd(23), 23 * 23)

        ' Now iterate through, adding one to the end of the list. Existing items should be updated to be divided by their 
        ' key  and a new item will be added that is the square of its key.
        For i As Integer = 1 To HIGHNUMBER + 1

            cd.AddOrUpdate(i, i * i, Function(k, v)
                                         Return v / i
                                     End Function)
        Next

        Console.WriteLine("The square root of 529 is {0} (should be {1})", cd(23), 529 / 23)
        Console.WriteLine("The square of 65 is {0} (should be {1})", cd(HIGHNUMBER + 1), ((HIGHNUMBER + 1) * (HIGHNUMBER + 1)))

    End Sub
End Class

For modifications and write operations to the dictionary, ConcurrentDictionary<TKey,TValue> uses fine-grained locking to ensure thread safety. (Read operations on the dictionary are performed in a lock-free manner.) The addValueFactory and updateValueFactory delegates may be executed multiple times to verify the value was added or updated as expected. However, they are called outside the locks to avoid the problems that can arise from executing unknown code under a lock. Therefore, AddOrUpdate is not atomic with regards to all other operations on the ConcurrentDictionary<TKey,TValue> class.

See also

• Thread-Safe Collections
• How to: Add and Remove Items from a ConcurrentDictionary

Source:

ConcurrentDictionary.cs

Source:

ConcurrentDictionary.cs

Source:

ConcurrentDictionary.cs

public:
generic <typename TArg>
 TValue AddOrUpdate(TKey key, Func<TKey, TArg, TValue> ^ addValueFactory, Func<TKey, TValue, TArg, TValue> ^ updateValueFactory, TArg factoryArgument);

public TValue AddOrUpdate<TArg> (TKey key, Func<TKey,TArg,TValue> addValueFactory, Func<TKey,TValue,TArg,TValue> updateValueFactory, TArg factoryArgument);

member this.AddOrUpdate : 'Key * Func<'Key, 'Arg, 'Value> * Func<'Key, 'Value, 'Arg, 'Value> * 'Arg -> 'Value

Public Function AddOrUpdate(Of TArg) (key As TKey, addValueFactory As Func(Of TKey, TArg, TValue), updateValueFactory As Func(Of TKey, TValue, TArg, TValue), factoryArgument As TArg) As TValue

Type Parameters

Parameters

Returns

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).

Exceptions

Remarks

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.

For modifications and write operations to the dictionary, ConcurrentDictionary<TKey,TValue> uses fine-grained locking to ensure thread safety. (Read operations on the dictionary are performed in a lock-free manner.) The addValueFactory and updateValueFactory delegates may be executed multiple times to verify the value was added or updated as expected. However, they are called outside the locks to avoid the problems that can arise from executing unknown code under a lock. Therefore, AddOrUpdate is not atomic with regards to all other operations on the ConcurrentDictionary<TKey,TValue> class.