给牛宝宝起个小名

書(shū)名： Microsoft Windows Workflow Foundation 4.0 Cookbook
作者名： Andrew Zhu
本章字?jǐn)?shù)： 336字
更新時(shí)間： 2021-04-13 17:00:34

Creating a WF program using C# Code

In this task, we will create the same "HelloWorkflow" function workflow using pure C# code, beginning from a Console Application.

How to do it...

Create a Console Application project:
Create a new Console Application project under the Chapter01 solution. Name the project HelloCodeWorkflow. The following screenshot shows the Console Application new project dialog:
Add reference to the System.Activities assembly:
By default, a new Console Application doesn't have reference to the System.Activities assembly, due to which we need to perform this step.

Create workflow definition code:

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

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

namespace HelloCodeWorkflow {
    class Program {
        static void Main(string[] args) {
            WorkflowInvoker.Invoke(new HelloWorkflow());
        }
    }

    public class HelloWorkflow:Activity {
        public HelloWorkflow() {
            this.Implementation = () => new Sequence {
                Activities = {
                    new WriteLine(){Text="Hello Workflow"}
                }
            };
        }
    }
}

Run it:
Set HelloCodeWorkflow as StartUp project and press Ctrl+F5 to run it. As expected, the result should be just like the previous result shown.

How it works...

We use the following namespaces:

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

Because WorflowInvoker class belongs to System.Activities namespace. Sequence activity, WriteLine activity belongs to System.Activities.Statements. namespace.

public class HelloWorkflow:Activity {
    public HelloWorkflow() {
        this.Implementation = () => new Sequence {
            Activities = {
                new WriteLine(){Text="Hellow Workflow"}
            }
        };
    }
}

By implementing a class inherited from Activity, we define a workflow using imperative code.

WorkflowInvoker.Invoke(s);

This code statement loads a workflow instance up and runs it automatically. The WorkflowInvoker.Invoke method is synchronous and invokes the workflow on the same thread as the caller.

There's more

WF4 also provides us a class DynamicActivity by which we can create a workflow instance dynamically in the runtime. In other words, by using DynamicActivity, there is no need to define a workflow class before initializing a workflow instance. Here is some sample code:

public static DynamicActivity GetWF() {
    return new DynamicActivity() {
        Implementation = () => new Sequence() {
            Activities ={
                new WriteLine(){Text="Hello Workflow"}
            }
        }
    };
}

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Microsoft Windows Workflow Foundation 4.0 Cookbook