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我正在针对 .NET 3.5 的 VS2010 中创建自定义工作流活动。DLL 实际上是在 Microsoft System Center Service Manager 自定义工作流程中使用的，但我认为这不是我的问题。

我有一个公共字符串属性，用户输入活动应该使用的字符串。但是，当 WF 运行时，它会报错“值不能为空”。我想定位它是我的代码还是其他东西。

当我们将自定义活动拖到设计器上时，我可以在该属性的设计器上输入字符串文本。

public static DependencyProperty ChangeRequestStageProperty = DependencyProperty.Register("ChangeRequestStage", typeof(String), typeof(UpdateChangeRequestStage));

    [DescriptionAttribute("The value to set the ChangeRequestStage Property in the ChangeRequest Extension class.")]
    [CategoryAttribute("Change Request Extension")]
    [BrowsableAttribute(true)]
    [DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Visible)]
    public String Stage
    {
        get { return ((String)(base.GetValue(UpdateChangeRequestStage.ChangeRequestStageProperty))); }
        set { base.SetValue(UpdateChangeRequestStage.ChangeRequestStageProperty, value); }
    }

    protected override ActivityExecutionStatus Execute(ActivityExecutionContext executionContext)
    {
        EnterpriseManagementGroup emg = CreateEMG();

        //System.WorkItem.ChangeRequest Extension - ClassExtension_928bec0a_cac4_4a0a_bd89_7146c9052fbe
        ManagementPackClass mpcChangeRequest = emg.EntityTypes.GetClass(new Guid("8c6c6057-56ad-3862-47ec-dc0dde80a071"));

        //System.WorkItemContainsActivity Relationship Class
        ManagementPackRelationship workItemContainsActivityRelationship = emg.EntityTypes.GetRelationshipClass(new Guid("2DA498BE-0485-B2B2-D520-6EBD1698E61B"));

        EnterpriseManagementObject changeRequest = null;

        //Loop thru each emo (Change Request in this case), and assign it. There will never be more than 1 emo returned
        foreach (EnterpriseManagementObject obj in emg.EntityObjects.GetRelatedObjects<EnterpriseManagementObject>(executionContext.ContextGuid, workItemContainsActivityRelationship, TraversalDepth.OneLevel, ObjectQueryOptions.Default))
        { changeRequest = obj; }

        EnterpriseManagementObjectProjection emop = new EnterpriseManagementObjectProjection(changeRequest);

        if (emop != null)
        { emop.Object[mpcChangeRequest, "ChangeRequestStage"].Value = Stage; }

        emop.Commit();

        return base.Execute(executionContext);
    }

由于它收到“值不能为空”错误，我猜它在这一行：

emop.Object[mpcChangeRequest, "ChangeRequestStage"].Value = Stage;

我将测试并查看硬编码值是否有效。有任何想法吗？在这里输入代码

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2 回答 2

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试试这个

if (emop != null && emop.Object[mpcChangeRequest, "ChangeRequestStage"] != null)
   emop.Object[mpcChangeRequest, "ChangeRequestStage"].Value = Stage
于 2010-11-30T14:54:45.173 回答
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我不想让这个问题悬而未决，所以我正在更新它关于我如何解决这个问题（很久以前）。

我没有使用EnterpriseManagementObjectProjection（emop），而是使用标准EnterpriseManagementObject（emo）。从那里，我能够从上面遵循类似的格式：

ManagementPackClass mpcChangeRequest = emg.EntityTypes.GetClass(new Guid("8c246fc5-4e5e-0605-dc23-91f7a362615b"));
changeRequest[mpcChangeRequest, "ChangeRequestStage"].Value = this.Stage;
changeRequest.Commit();
于 2011-05-10T14:53:15.363 回答