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AsyncOperation.UserSuppliedState Property

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Definition

Namespace:
System.ComponentModel
Assemblies:
System.dll, System.ComponentModel.EventBasedAsync.dll
Assembly:
System.ComponentModel.EventBasedAsync.dll
Assembly:
System.dll
Assembly:
netstandard.dll
Source:
AsyncOperation.cs
Source:
AsyncOperation.cs
Source:
AsyncOperation.cs

Gets or sets an object used to uniquely identify an asynchronous operation.

public:
 property System::Object ^ UserSuppliedState { System::Object ^ get(); };
public object UserSuppliedState { get; }
public object? UserSuppliedState { get; }
member this.UserSuppliedState : obj
Public ReadOnly Property UserSuppliedState As Object

Property Value

Object

The state object passed to the asynchronous method invocation.

Examples

The following code example demonstrates using UserSuppliedState to track the lifetime of asynchronous operations. This code example is part of a larger example provided for the System.ComponentModel.AsyncOperationManager class.

// This method cancels a pending asynchronous operation.
public void CancelAsync(object taskId)
{
    AsyncOperation asyncOp = userStateToLifetime[taskId] as AsyncOperation;
    if (asyncOp != null)
    {   
        lock (userStateToLifetime.SyncRoot)
        {
            userStateToLifetime.Remove(taskId);
        }
    }
}

' This method cancels a pending asynchronous operation.
Public Sub CancelAsync(ByVal taskId As Object)

    Dim obj As Object = userStateToLifetime(taskId)
    If (obj IsNot Nothing) Then

        SyncLock userStateToLifetime.SyncRoot

            userStateToLifetime.Remove(taskId)

        End SyncLock

    End If

End Sub

Remarks

If your class supports multiple asynchronous methods or multiple invocations of a single asynchronous method, clients will need a way to determine which asynchronous task is raising events. Your MethodNameAsync method should take a parameter of type Object that will act as a task ID. You will use this task ID when you call the AsyncOperationManager.CreateOperation, method and this will associate the client's task ID with a particular invocation of your asynchronous operation. This task ID is made available to your implementation through the UserSuppliedState property.

Caution

Client code must be careful to provide a unique value for the UserSuppliedState property. Non-unique task IDs may cause your implementation to report progress and other events incorrectly. Your code should check for a non-unique task ID and raise an ArgumentException if one is detected.

Applies to

See also