tailieunhanh - Professional Visual Basic 2010 and .neT 4 phần 8

Các thiết lập được sử dụng để tạo ra các trang nội dung trong dự án mẫu được thể hiện trong hình 22-4. Nhấp vào nút Add sẽ trả về một hộp thoại cho phép bạn chọn một trang chủ để liên kết với tập tin mới, như thể hiện trong hình 22-5. | 888 I CHAPTER 26 WINDOWS WORKFLOW FOUNDATION continued ACTIVITY DESCRIPTION Switch T Works like the VB case statement. Switches the flow through a workflow based on the value of a variable or condition. While Works like the VB while loop. Performs a child activity use a sequence if you need multiple steps while a condition is true. TerminateWorkflow Stops the workflow before the end of the workflow is reached. This is useful in the event of errors in the workflow or if the data input doesn t allow for completion. Also used for flowchart workflows as a means of completion. Activities that communicate with external code These activities are either called by external code to initiate a workflow or used to call to external code as part of a workflow. This category also includes activities that communicate with external systems to persist the workflow state. ACTIVITY DESCRIPTION Receive Receives a one-way WCF message ReceiveAndSendReply Receives a WCF message and sends back a result Send Sends a one-way WCF message SendAndReceiveReply Sends a WCF message and waits for a result Persist Saves the current state of the workflow. This is very useful for long-running workflows as it enables you to save the current state of the workflow saving memory. You can then reload the workflow as it was persisted as needed later. Transaction activities These activities group a number of other activities together into some logical element. This is usually done to mark a number of activities that participate in a transaction. ACTIVITY DESCRIPTION CancellationScope Marks the boundaries of a set of activities to perform if a process is cancelled. Typically this would be used to close any handles undo any partially completed steps etc. CompensableActivity Marks the boundaries of an activity that may be undone. This activity groups one or more actions to be performed. In addition it contains actions to undo whatever steps may have already been performed. This is typically to enable