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
Chapter01solution. Name the projectUseInArgument.Author the WF program:
Create a workflow as shown in the following screenshot:
Write code to host the workflow.
Open the
Program.csfile 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
UseInArgumentas 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)
)
}
}
};
}
}