不朽的情缘进入官方系统

書名： Microsoft Windows Workflow Foundation 4.0 Cookbook
作者名： Andrew Zhu
本章字數： 349字
更新時間： 2021-04-13 17:00:34

Initializing a WF program using InArguments

In this task, we will create a WF program that accepts arguments when initialized in the WF host. In WF4, we can use InArguments to define the way data flows into an activity.

How to do it...

Create a workflow project:
Create a new Workflow Console Application under the Chapter01 solution. Name the project UseInArgument .
Author the WF program:
Create a workflow as shown in the following screenshot:

Write code to host the workflow.

Open the Program.cs file and change the host code as follows:

using System.Activities;
using System.Activities.Statements;

namespace UseInArgument {
class Program {
        static void Main(string[] args) {
            WorkflowInvoker.Invoke(new Workflow1() 
            {
                FirstName="Andrew",
                SecondName="Zhu"
            });
        }
    }
}

Run it:
Set UseInArgument 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 following message:

How it works...

Consider the following statement from the code we saw in the preceding section:

FirstName="Andrew"

FirstName is an InArgument type, but how can we assign a string to InArgument without any explicit cast? This is because InArgument is declared with an attribute System.ComponentModel.TypeConverterAttribute(System.Activities.XamlIntegration.InArgumentConverter). The class inheritance is shown in the following diagram:

It is the InArgumentConverter that makes assigning a string to an InArgument possible. If we want to know more about TypeConverter, we can check MSDN the reference at http://msdn.microsoft.com/en-us/library/system.componentmodel.typeconverter.aspx

There's more

In WF3/3.5, we can pass values to Workflow wrapped in a Dictionary<T> object. This also applies to WF4.

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

namespace UseInArgument {
    class Program {
        static void Main(string[] args) {
            IDictionary<string, object> inputDictionary = 
                new Dictionary<string, object>() 
            { 
                {"FirstName","Andrew"},
                {"SecondName","Zhu"}
            };
            WorkflowInvoker.Invoke(new Workflow1(), 
                                   inputDictionary);
        }
    }
}

If we are creating workflows using imperative code, we can use InArgument in the following way:

public class WorkflowInCode:Activity {
    public InArgument<string> FirstName { get; set; }
    public InArgument<string> SecondName { get; set; }
    public WorkflowInCode() {
        this.Implementation = () => new Sequence() {
            Activities = {
                new WriteLine(){
                    Text=new InArgument<string>(
                            activityContext=>"My name is "+FirstName.Get(activityContext)
                        )
                },
                new WriteLine(){
                    Text=new InArgument<string>(
                            ActivityContext=>SecondName.Get(ActivityContext)
                        )
                }
            }
        };
    }
}

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