In this lesson, you will learn how to check whether or not a property value satisfies a particular rule. For this purpose, the DemoTask.Status property and the MarkCompleted Action will be used. This action should not be executed if the current task status is "NotStarted". Thus, the rule will be checked when executing the MarkCompleted Action.
在本课中，您将学习如何检查属性值是否满足特定规则。为此，将使用 DemoTask.Status 属性和标记完成操作。如果当前任务状态为"未启动"，则不应执行此操作。因此，在执行"标记完成操作"时将检查规则。
Note
Before proceeding, take a moment to review the following lessons.
- Implement Property Value Validation in Code (XPO/EF)
- Place an Action in a Different Location
注意
在继续之前，请花点时间复习以下课程。
- 在代码中实现属性值验证 （XPO/EF）
- 将操作放置在其他位置
The validation functionality is provided by the Validation Module that was added in the Implement Property Value Validation in Code (XPO) lesson. When this module is added to the MySolution.Module project, the Validation node is available in the Application Model. This node defines the validation Contexts and Rules used in your application. You can use the Model Editor to add Rules and specify Contexts.
验证功能由在代码 （XPO） 课程中添加的验证模块提供。当此模块添加到 MySolution.模块项目时，验证节点在应用程序模型中可用。此节点定义应用程序中使用的验证上下文和规则。您可以使用模型编辑器添加规则并指定上下文。
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Invoke the Model Editor for the MySolution.Module project. Navigate to the Validation | Rules node. It already contains child nodes that define the rules to be checked. For example, it may contain the "RuleRequiredField for Position.Title" rule that was implemented in the Implement Property Value Validation in Code (XPO) lesson. To add a new rule that checks specific criteria, right-click the Rules node and select Add... | RuleCriteria.
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调用 MySolution.模块项目的模型编辑器。导航到验证 |规则节点。它已包含定义要检查的规则的子节点。例如，它可能包含在代码 （XPO） 课程中实现属性值验证中的"位置.Title.Title"规则。要添加检查特定条件的新规则，请右键单击"规则"节点并选择"添加..." |规则标准。
Note 注意
The descriptions of all available rule types are available in the Validation Rules topic.
所有可用规则类型的说明在验证规则主题中可用。
- For the newly created node, set the TargetType to "MySolution.Module.BusinessObjects.DemoTask", and set the Criteria property to "Status != 'NotStarted'". Set the ID property to "TaskIsNotStarted", TargetContextIDs to "MarkCompleted" and CustomMessageTemplate to "Cannot set the task as completed because it has not started".
- 对于新创建的节点，将目标类型设置为"MySolution.Module.业务对象.演示任务"，并将"条件"属性设置为"状态！= "未启动"。将 ID 属性设置为"TaskIsNot 已启动"，将目标上下文ID 设置为"标记为已完成"，将自定义消息模板设置为"无法将任务设置为已完成，因为它尚未启动"。
Note 注意
The Criteria property value must be specified using the Criteria Language Syntax. To simplify this task, you can invoke the Filter Builder dialog by clicking the ellipsis button (
) to the right of the Criteria value. Within this dialog, you can visually design a criteria expression.
必须使用"条件语言语法"指定"条件"属性值。要简化此任务，可以通过单击条件值右侧的省略号按钮 （EllipsisButton） 来调用"筛选器生成器"对话框。在此对话框中，您可以直观地设计条件表达式。
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The TargetContextIDs property is set to "MarkCompleted". This means that the rule will be checked when executing the Action whose ValidationContexts property is set to "MarkCompleted". So, set the Mark Completed Action's ValidationContexts property (in the ActionDesign | Actions | Task.MarkCompleted node) to "MarkCompleted".
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"目标上下文"属性设置为"标记已完成"。这意味着在执行其验证上下文属性设置为"标记完成"的操作时，将检查规则。因此，设置"标记已完成操作的验证上下文"属性（在操作设计 |操作 |任务.标记已完成节点）到"标记已完成"。
Note 注意
You can also use the Save or Delete contexts, which are available by default. Rules with these contexts are validated when an object is saved or deleted, respectively (see Validation Rules).
您还可以使用默认可用的"保存或删除"上下文。分别保存或删除对象时，将验证具有这些上下文的规则（请参阅验证规则）。
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Run the WinForms or ASP.NET application. Assign the "Not Started" value to the Status property of one of the existing DemoTask objects. Click the MarkCompleted button. The following Validation Error dialog will be displayed.
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运行 WinForms 或ASP.NET应用程序。将"未启动"值分配给现有演示任务对象之一的状态属性。单击"标记已完成"按钮。将显示以下验证错误对话框。
Note 注意
Generally, you can add the required rule to a class or property in code (see Implement Property Value Validation in Code (EF \ XPO)). The approach defined above is useful when the class sources are inaccessible.
通常，可以将所需的规则添加到代码中的类或属性（请参阅在代码中实现属性值验证 （EF = XPO）。）。当类源无法访问时，上面定义的方法非常有用。
You can see the changes made in this lesson in the Model Editor invoked for the Model.DesignedDiffs.xafml file located in the Main Demo | MainDemo.Module project. The MainDemo application is installed in %PUBLIC%\Documents\DevExpress Demos 19.2\Components\eXpressApp Framework\MainDemo by default. The ASP.NET version is available online at http://demos.devexpress.com/XAF/MainDemo/
您可以在本课中为模型调用的模型编辑器中所做的更改。主演示模块项目。主演示应用程序安装在%PUBLIC%\Documents\DevExpress Demos 19.2\Components\eXpressApp Framework\MainDemo by default. The ASP.NET version is available online at http://demos.devexpress.com/XAF/MainDemo/
.