ConcurrentDictionary<TKey, TValue>.TryRemove Method

Attempts to remove and return the value that has the specified key from the System.Collections.Concurrent.ConcurrentDictionary<TKey, TValue>.

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

public bool TryRemove(
	TKey key,
	out TValue value
)

Parameters

key
Type: TKey

The key of the element to remove and return.

value
Type: TValue

When this method returns, contains the object removed from the System.Collections.Concurrent.ConcurrentDictionary<TKey, TValue>, or the default value of the TValue type if key does not exist.

Return Value

Type: System.Boolean
true if the object was removed successfully; otherwise, false.

ExceptionCondition
ArgumentNullException

key is null.

The following example shows how to call the ConcurrentDictionary<TKey, TValue>.TryRemove method:

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!");
        }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 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

.NET for Windows Phone apps

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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