WorkflowItemPresenter内容在生成时消失

所有的,
在自定义活动中,当我将活动放入 WorkflowItemPresenter , 保存编译 ,我的活动突然 消失 我也不知道为什么。我可能在某个地方犯了点小错误,但我看不到。我已经返回并确保我的代码符合要求,删除并重新添加了包含自定义活动的程序集,这可能只是个侥幸。之后,当我尝试从引用自定义活动的项目编译时。它跑了,但却丢了一个 ArgumentNullException . 我试过传递bools,conditionals,或者只是选择其他,结果都是一样的。在这种情况下,有没有任何关于故障排除的建议或明显的东西丢失?

这是我的病情参考资料 ActivityFunc <bool> Condition .

<sap:WorkflowItemPresenter
                        HintText="Add Trigger conditional activities here"
                        Item="{Binding Path=ModelItem.Condition.Handler}" 
                        Height="40"
                        />

这是我对在条件返回true后要调度的子级的引用 public ActivityAction Child .

<sap:WorkflowItemPresenter
                        HintText="Add activies that happen on trigger firing"
                        Item="{Binding Path=ModelItem.Child.Handler}" 
                        Height="40"/>

这是我的定制活动

[Designer(typeof(TriggerDesigner)),
Description("Creates a Trigger for use by trigger conditionals"),    ToolboxCategory(ToolboxCategoryAttribute.Trigger),
ToolboxBitmap(typeof(Shaolin.Activities.ToolboxIconAttribute), "ToolboxIcons.CreateImportContext")]
public sealed class Trigger : NativeActivity
{
    /// <summary>
    /// The initial Condition that determines if the trigger should be scheduled
    /// </summary>
    /// <value>The condition.</value>
    public ActivityFunc<bool> Condition { get; set; }

    /// <summary>
    /// The resulting action that is scheduled if the Condition is true
    /// </summary>
    /// <value>The child.</value>
    public ActivityAction Child { get; set; }

    /// <summary>
    /// Gets or sets the value holding whether or not the trigger matches the condition
    /// </summary>
    /// <value>The type of the match.</value>
    public MatchType MatchType{ get; set; }

    /// <summary>
    /// Perform evaluation of Condition; if is true then schedules Child
    /// </summary>
    /// <param name="context">The execution context in which the activity executes.</param>
    protected override void Execute(NativeActivityContext context)
    {
        context.ScheduleFunc<bool>(this.Condition, new CompletionCallback<bool>(OnConditionComplete));
    }

    /// <summary>
    /// Called from Execute when Condition evaluates to true.
    /// </summary>
    /// <param name="context">The context.</param>
    /// <param name="instance">The instance.</param>
    /// <param name="result">if set to <c>true</c> [result].</param>
    public void OnConditionComplete(NativeActivityContext context, ActivityInstance instance, bool result)
    {
        //check if Condition evaluation returns true
        if (result) 
        {
            //If so then schedule child Activity
            context.ScheduleAction(Child);
        }
    }
}

}