ParallelForEach<T> Class

.NET Framework (current version)

Enumerates the elements of a collection and executes an embedded statement for each element of the collection in parallel.

Namespace:   System.Activities.Statements
Assembly:  System.Activities (in System.Activities.dll)


public sealed class ParallelForEach<T> : NativeActivity

Type Parameters


The type of the values provided in the Values collection.


Creates a new instance of the ParallelForEach<T> class.


The ActivityAction that is executed once for every value contained in the Values collection.


Gets the identifier of the cache that is unique within the scope of the workflow definition.(Inherited from Activity.)


Evaluated after each iteration completes.


Gets or sets an optional friendly name that is used for debugging, validation, exception handling, and tracking.(Inherited from Activity.)


Gets an identifier that is unique in the scope of the workflow definition.(Inherited from Activity.)


Gets or sets the implementation version of the activity.(Inherited from NativeActivity.)


The collection of values used as parameters for each iteration of the activity contained in the Body.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Indicates whether the DisplayName property should be serialized.(Inherited from Activity.)


Returns a String that contains the Id and DisplayName of the Activity.(Inherited from Activity.)

The embedded statements are scheduled together and run asynchronously, but unless the scheduled activites themselves are asynchronous (such as messaging activities, InvokeMethod, or activities that derive from AsyncCodeActivity), they do not run on separate threads, so each successive activity will only execute when the previously scheduled activity completes or goes idle. If none of the child activities of this activity are asynchronous or go idle, this activity execute in the same way that a ForEach<T> activity does.

The following code sample demonstrates creating a ParallelForEach<T> activity. This example is from the Corporate Purchase Process sample.

// invite all vendors and wait for their proposals
new ParallelForEach<Vendor>
    DisplayName = "Get vendor proposals",
    Values = new InArgument<IEnumerable<Vendor>>(ctx =>this.Rfp.Get(ctx).InvitedVendors),
    Body = new ActivityAction<Vendor>()
        Argument = iterationVariableVendor,
        Handler = new Sequence
            Variables = { tmpValue },
            Activities =
                // waits for a vendor proposal (creates a bookmark for a vendor)
                new WaitForVendorProposal 
                    VendorId = new LambdaValue<int>(ctx =>iterationVariableVendor.Get(ctx).Id) ,
                    Result = new OutArgument<double>(tmpValue)

                // after the vendor proposal is received, it is registered in the Request for Proposals
                new InvokeMethod
                    TargetObject = new InArgument<RequestForProposal>(ctx =>this.Rfp.Get(ctx)),
                    MethodName = "RegisterProposal",
                    Parameters = 
                        new InArgument<Vendor>(iterationVariableVendor),
                        new InArgument<double>(tmpValue)

.NET Framework
Available since 4.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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