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書名： Microsoft Windows Workflow Foundation 4.0 Cookbook
作者名： Andrew Zhu
本章字數： 300字
更新時間： 2021-04-13 17:00:35

Creating a WF program using InOutArgument

In this task, we will create a WF program using InOutArgument. This type of argument is used to receive values and is also used to pass values out to the caller (WF host).

How to do it…

Create a workflow project:
Create a new Workflow Console Application under the Chapter01 solution and name the project as UseInOutArgument.
Author a workflow:
Create an InOutArgument type argument: InOutMessage. Author a WF program as shown in the following screenshot. In the Assign activity textbox, type InOutMessage = "Now, I am an OutMessage".

Write code to host the workflow:

Open the Program.cs file and alter the code as shown:

using System;
using System.Activities;
using System.Activities.Statements;
using System.Collections.Generic;

namespace UseInOutArgument{
    class Program{
        static void Main(string[] args){
            IDictionary<string, object> input =
                new Dictionary<string, object>() 
            { 
                {"InOutMessage","Now, I am InMessage"}
            };
            IDictionary<string,object> output=
                WorkflowInvoker.Invoke(new Workflow1(),input);
            Console.WriteLine(output["InOutMessage"]);
        }
    }
}

Run it:
Set UseInOutArgument as Startup project. Press Ctrl+F5 to build and run the workflow without debugging. The application should run in a console window and print the message as shown in the following screenshot:

How it works...

The following code block initializes the InArgument value:

IDictionary<string, object> input =
                new Dictionary<string, object>() 
            { 
                {"InOutMessage","Now, I am InMessage"}
            };

This statement will run the workflow program with the input dictionary.

IDictionary<string,object> output=
                WorkflowInvoker.Invoke(new Workflow1(),input);

The string Now, I am InMessage is printed by the workflow. The string Now, I am an OutMessage is a message altered in the workflow and passed to the host and then printed by the host program.

There's more...

We cannot assign a string to InOutArgument directly, and the following style of parameter initialization is not allowed:

IDictionary<string, object> output =
    WorkflowInvoker.Invoke(new Workflow1() 
    { 
        InOutMessage="Now,I am InMessage"
    });

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Microsoft Windows Workflow Foundation 4.0 Cookbook