How to: Create a Workflow Service That Calls Another Workflow Service

  • Artigo

This topic applies to Windows Workflow Foundation 4 (WF4).

It is sometimes necessary for a workflow service to obtain information from another workflow service. This topic demonstrates how to call one workflow service from another. In this topic, we’ll create two workflow services; one that has a method that reverses the input string, and another that converts the input string to uppercase after reversing the string that uses the first service.

To create the Reverser workflow service

  1. Run Visual Studio 2010 as an administrator.

  2. Select File, New Project. Under the Workflow node in the Installed Templates pane, select WCF Workflow Service Application. Name the solution NestedServices and then click OK.

  3. Under Servers, make sure that Use Local IIS Web Server is selected. Click Create Virtual Directory. Click OK in the dialog box stating that the virtual directory was successfully created.

  4. In Solution Explorer, rename Service1.xamlx to StringReverserService.xamlx.

  5. On the Project Properties page for the new project, click the Web tab. Set the Start Action to Specific Page, and select StringReverserService.xamlx as the page to start.

  6. Open StringReverserService.xamlx in the designer and delete the existing ReceiveRequest and SendReply activities, and then drag a ReceiveAndSendReply activity into the existing sequence activity.

    1. Set the OperationName to ReverseString.

    2. Set the ServiceContractName to IReverseString.

    3. Select the CanCreateInstance check box.

  7. Select the SequentialService activity, and then click the Variables tab at the bottom of the designer. Create two new variables named StringToReverse and ReversedStringToReturn of type String.

  8. Click the Define link in the Receive activity. Click the Parameters, and create a parameter named InputString of type String that assigns to StringToReverse.

  9. Click the Define link in the SendReplyToReceive activity. Click the Parameters, and create a parameter named ReversedString of type String, assigned to ReversedStringToReturn.

  10. To implement the logic for the service, create a new class in the project called StringLibrary. Replace the class definition with the following code.

    public class StringLibrary
    {
        public static String ReverseString(string StringToReverse)
        {
            char[] charArray = StringToReverse.ToCharArray();
            Array.Reverse(charArray);
            return new String(charArray);
        }
    }

  11. To call the ReverseString method on the input, drag an InvokeMethod activity from the toolbox to the space between the Receive and SendReply activities. Set the properties of the activity as follows:

    1. MethodName: ReverseString

    2. Result: ReversedStringToReturn

    3. Parameters: Create a new parameter with a Direction of In, a Type of String, and a Value of StringToReverse.

    4. TargetType: NestedServices.StringLibrary

  12. Test the service by pressing F5. In the WCF Test Client that appears, double-click the ReverseString() method. In the Request pane, enter Sample for the Value of the InputString parameter. Click Invoke. The service should return "elpmaS".

To create the UpperCaser workflow service

  1. Right-click the NestedServices project and select Add, New Item. In the Workflow node, select WCF Workflow Service, and name the new service UpperCaserService. Click Add. This should add a new workflow service called UpperCaserService.xamlx to the project.

  2. Open UpperCaserService.xamlx in the designer and delete the existing ReceiveRequest and SendReply activities, and drag a ReceiveAndSendReply activity into the existing sequence activity.

    1. Set the OperationName to UpperCaseString.

    2. Set the ServiceContractName to IUpperCaseString.

    3. Select the CanCreateInstance check box.

  3. Select the SequentialService activity, and then click the Variables tab at the bottom of the designer. Create three new variables named StringToUpper, StringToReverse, and StringToReturn of type String.

  4. Click the Define link in the Receive activity. Click the Parameters, and create a parameter named InputString of type String that assigns to StringToUpper.

  5. Click the Define link in the SendReplyToReceive activity. Click the Parameters, and create a parameter named ModifiedString of type String, assigned to StringToReturn.

  6. To implement the logic for the service, create a new method in the StringLibrary class using the following code.

            public static String UpperCaseString(string StringToUpperCase)
        {
             return StringToUpperCase.ToUpper();

        }

  7. To call the UpperCaseString method on the input, drag an InvokeMethod activity from the toolbox to the space between the Receive and SendReply activities. Set the properties of the activity as follows:

    1. MethodName: UpperCaseString

    2. Result: StringToReverse

    3. Parameters: Create a new parameter with a Direction of In, a Type of String, and a Value of StringToUpper.

    4. TargetType: NestedServices.StringLibrary

  8. We’ll now call the first service on the modified string. Right-click the project and select Add Service Reference. Add a service reference to the service at https://localhost/NestedServices/StringReverserService.xamlx and build the project to create a custom activity to access the first Web service.

  9. Drag an instance of the new activity onto the workflow, between the InvokeMethod activity and the SendReplyToReceive activities. Assign the variable StringToReverse to the InputString property of the new activity, and the variable StringToReturn to the StringToReturn property.

  10. Open the Properties page for the NestedServices project, and change the Specific Page in the Web tab to UpperCaserService.xamlx.

  11. Test the service by pressing F5. In the WCF Test Client that appears, double-click the ReverseString() method. In the Request pane, enter Sample for the Value of the InputString parameter. Click Invoke. The service should return "ELPMAS".

To create a client to call the services

  1. Add a new Console application project called Client to the solution.

  2. Right-click the Client project and select Add Service Reference. In the window that appears, click Discover. Select StringReverserService.xamlx, and enter ReverseService as the namespace. Click OK.

  3. Replace the Main method in Program.cs with the following code.

    static void Main(string[] args)
{
    Console.Write("Input string to process:");
    String input = Console.ReadLine();
    var service = new ReverseService.ReverseStringClient();
    Console.WriteLine("Output from service: {0}", service.ReverseString(input));
    Console.ReadKey();
}