ConcurrentDictionary<TKey,TValue>.TryUpdate メソッド

定義

名前空間:

System.Collections.Concurrent

アセンブリ:

System.Collections.Concurrent.dll

ソース:

ConcurrentDictionary.cs

key での既存の値が comparisonValue と等しい場合は、key に関連付けられている値を newValue に更新します。

public:
 bool TryUpdate(TKey key, TValue newValue, TValue comparisonValue);

public bool TryUpdate (TKey key, TValue newValue, TValue comparisonValue);

member this.TryUpdate : 'Key * 'Value * 'Value -> bool

Public Function TryUpdate (key As TKey, newValue As TValue, comparisonValue As TValue) As Boolean

パラメーター

key

TKey

値を comparisonValue と比較し、場合によっては置き換えるキー。

newValue

TValue

比較した結果が等しい場合に、指定した key を持つ要素の値を置き換える値。

comparisonValue

TValue

指定した key を持つ要素の値と比較する値。

戻り値

Boolean

true を持つ値が key に等しかったため、comparisonValue に置き換えられた場合は newValue。それ以外の場合は false。

例外

ArgumentNullException

key が nullです。

例

次の例は、 メソッドを呼び出す方法を TryUpdate 示しています。

class CD_TryXYZ
{
        // Demonstrates:
        //      ConcurrentDictionary<TKey, TValue>.TryAdd()
        //      ConcurrentDictionary<TKey, TValue>.TryUpdate()
        //      ConcurrentDictionary<TKey, TValue>.TryRemove()
        static void Main()
        {
            int numFailures = 0; // for bookkeeping

            // Construct an empty dictionary
            ConcurrentDictionary<int, String> cd = new ConcurrentDictionary<int, string>();

            // This should work
            if (!cd.TryAdd(1, "one"))
            {
                Console.WriteLine("CD.TryAdd() failed when it should have succeeded");
                numFailures++;
            }

            // This shouldn't work -- key 1 is already in use
            if (cd.TryAdd(1, "uno"))
            {
                Console.WriteLine("CD.TryAdd() succeeded when it should have failed");
                numFailures++;
            }

            // Now change the value for key 1 from "one" to "uno" -- should work
            if (!cd.TryUpdate(1, "uno", "one"))
            {
                Console.WriteLine("CD.TryUpdate() failed when it should have succeeded");
                numFailures++;
            }

            // Try to change the value for key 1 from "eine" to "one"
            //    -- this shouldn't work, because the current value isn't "eine"
            if (cd.TryUpdate(1, "one", "eine"))
            {
                Console.WriteLine("CD.TryUpdate() succeeded when it should have failed");
                numFailures++;
            }

            // Remove key/value for key 1.  Should work.
            string value1;
            if (!cd.TryRemove(1, out value1))
            {
                Console.WriteLine("CD.TryRemove() failed when it should have succeeded");
                numFailures++;
            }

            // Remove key/value for key 1.  Shouldn't work, because I already removed it
            string value2;
            if (cd.TryRemove(1, out value2))
            {
                Console.WriteLine("CD.TryRemove() succeeded when it should have failed");
                numFailures++;
            }

            // If nothing went wrong, say so
            if (numFailures == 0) Console.WriteLine("  OK!");
        }
}

// Demonstrates:
//      ConcurrentDictionary<TKey, TValue>.TryAdd()
//      ConcurrentDictionary<TKey, TValue>.TryUpdate()
//      ConcurrentDictionary<TKey, TValue>.TryRemove()

let mutable numFailures = 0 // for bookkeeping

// Construct an empty dictionary
let cd = ConcurrentDictionary<int, string>()

// This should work
if cd.TryAdd(1, "one") |> not then
    printfn "CD.TryAdd() failed when it should have succeeded"
    numFailures <- numFailures + 1

// This shouldn't work -- key 1 is already in use
if cd.TryAdd(1, "uno") then
    printfn "CD.TryAdd() succeeded when it should have failed"
    numFailures <- numFailures + 1

// Now change the value for key 1 from "one" to "uno" -- should work
if cd.TryUpdate(1, "uno", "one") |> not then
    printfn "CD.TryUpdate() failed when it should have succeeded"
    numFailures <- numFailures + 1

// Try to change the value for key 1 from "eine" to "one"
//    -- this shouldn't work, because the current value isn't "eine"
if cd.TryUpdate(1, "one", "eine") then
    printfn "CD.TryUpdate() succeeded when it should have failed"
    numFailures <- numFailures + 1

// Remove key/value for key 1.  Should work.
let mutable value1 = ""

if cd.TryRemove(1, &value1) |> not then
    printfn "CD.TryRemove() failed when it should have succeeded"
    numFailures <- numFailures + 1

// Remove key/value for key 1.  Shouldn't work, because I already removed it
let mutable value2 = ""

if cd.TryRemove(1, &value2) then
    printfn "CD.TryRemove() succeeded when it should have failed"
    numFailures <- numFailures + 1

// If nothing went wrong, say so
if numFailures = 0 then
    printfn "  OK!"

'Imports System.Collections.Concurrent

Class CD_TryXYZ

    ' Demonstrates:
    ' ConcurrentDictionary<TKey, TValue>.TryAdd()
    ' ConcurrentDictionary<TKey, TValue>.TryUpdate()
    ' ConcurrentDictionary<TKey, TValue>.TryRemove()
    Shared Sub Main()
        Dim numFailures As Integer = 0
        ' for bookkeeping
        ' Construct an empty dictionary
        Dim cd As ConcurrentDictionary(Of Integer, [String]) = New ConcurrentDictionary(Of Integer, String)()

        ' This should work
        If Not cd.TryAdd(1, "one") Then
            Console.WriteLine("CD.TryAdd() failed when it should have succeeded")
            numFailures += 1
        End If

        ' This shouldn't work -- key 1 is already in use
        If cd.TryAdd(1, "uno") Then
            Console.WriteLine("CD.TryAdd() succeeded when it should have failed")
            numFailures += 1
        End If

        ' Now change the value for key 1 from "one" to "uno" -- should work
        If Not cd.TryUpdate(1, "uno", "one") Then
            Console.WriteLine("CD.TryUpdate() failed when it should have succeeded")
            numFailures += 1
        End If

        ' Try to change the value for key 1 from "eine" to "one" 
        ' -- this shouldn't work, because the current value isn't "eine"
        If cd.TryUpdate(1, "one", "eine") Then
            Console.WriteLine("CD.TryUpdate() succeeded when it should have failed")
            numFailures += 1
        End If

        ' Remove key/value for key 1. Should work.
        Dim value1 As String = ""
        If Not cd.TryRemove(1, value1) Then
            Console.WriteLine("CD.TryRemove() failed when it should have succeeded")
            numFailures += 1
        End If

        ' Remove key/value for key 1. Shouldn't work, because I already removed it
        Dim value2 As String = ""
        If cd.TryRemove(1, value2) Then
            Console.WriteLine("CD.TryRemove() succeeded when it should have failed")
            numFailures += 1
        End If

        ' If nothing went wrong, say so
        If numFailures = 0 Then
            Console.WriteLine(" OK!")
        End If
    End Sub
End Class

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