tailieunhanh - microsoft press windows workflow foundation step by step phần 2

Tham khảo tài liệu 'microsoft press windows workflow foundation step by step phần 2', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 2 The Workflow Runtime After completing this chapter you will be able to Be able to host the workflow runtime in your applications Understand the basic capabilities of the WorkflowRuntime object Know how to start and stop the workflow runtime Be able to connect to the various workflow runtime events When you execute tasks in the Workflow Foundation WF environment something needs to oversee that execution and keep things straight. In WF that something is an object known as WorkflowRuntime. WorkflowRuntime starts individual workflow tasks. WorkflowRuntime fires events for different situations that pop up while your tasks execute. And WorkflowRuntime keeps track of and uses pluggable services you can hook in to the execution environment. We ll look at some of these pluggable services starting in Chapter 5 Workflow Tracking. The overall WF architecture is shown in Figure 2-1. Host Application Figure 2-1 WF architecture 23 24 Part I Introducing Windows Workflow Foundation WF WF and your application execute concurrently. In fact WF requires your application as a host. The host application might be a Windows Forms application a console application an Web application or even a Windows service. The WF runtime and your application execute together in a .NET AppDomain and there can be only one instance of WorkflowRuntime per AppDomain. Attempting to create a second instance of WorkflowRuntime in a single AppDomain results in an InvalidOperationException. You build workflow applications workflows by creating logical groupings of activities. These logical groupings work to complete the workflow task you require. When you host the workflow runtime you essentially hand the workflow your activities and tell it to execute them. This results in a workflow instance. The workflow instance is a currently executing workflow task which is itself composed of logically grouped activities. And as you recall from the first chapter activities can execute code you provide as .