Chapter 1: Workflow Program

In this chapter we will see how to create WF program with different methods.

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...

1. Create a Workflow project:
   Create a new Workflow Console Application under the Chapter01 solution. Name the project UseInArgument.
   
2. Author the WF program :
   Create a Workflow as shown in the following screenshot:
   
   
   
3. 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"

               });

           }

       }

   }
   
4. 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)

                            )

                }

            }

        };

    }

}