从xaml获取输入参数，并通过MVC3将其用于WF4中的动态活动

Question

我正在尝试创建一个可以在xaml中重用的本机活动，它基本上复制了WF3.x中的PolicyActivity的功能，WF3.x是一个带有图形用户界面的规则引擎，用于编辑规则。

我的问题是，当我调用WorkflowInvoker.Invoke时，它会说模型，也就是InArgument是Null，我知道这不是因为这段代码是作为返回活动的函数工作的，就像Frode Nilsen的博客中的那样：Using WF 4 as a Rules Engine我的问题是，我是否从Xaml活动中正确地获得了InArgument？

 public sealed class RuleSequenceAcitvity : NativeActivity<Sequence>
{
    private Sequence _sequence;
    InArgument<HomeIndexViewModel> Model { get; set; } //Same name as inArgument in xaml

    protected override void Execute(NativeActivityContext context)
    {
        populateSequence();
        var input = new Dictionary<string, object>();
        //The following line is giving me the Null Argument Exception
        var model = context.GetValue<HomeIndexViewModel>(this.Model);
        input.Add("Model", model);
        WorkflowInvoker.Invoke(_sequence, input);

    }

    private void populateSequence()
    {
        //get the list of rules from repository
        var rules = ObjectFactory.Container.GetInstance<IRuleRepository>().Rules.ToList();

        //Declare a dynamic property as the view model
        var inProperty = new DynamicActivityProperty
        {
            Name = "Model",
            Type = typeof(InArgument<HomeIndexViewModel>),
            Value = Model
        };
        var activity = new DynamicActivity() { Properties = { inProperty } };

        //Import references
        Common.AddVbSetting(activity);

        _sequence = new Sequence();
        activity.Implementation = () => _sequence;

        //Sort Descending - those added first are lowest priority
        var sortedRules = rules.OrderBy(x => x.Priority).ToList();

        foreach (var inRule in rules)
        {
            var outRule = RuleConverter.ToIfActivity(inRule);
            _sequence.Activities.Add(outRule);
        }

    }
}

}

Answer 1

你就快到了。

首先，您必须将您的InArgument<HomeIndexViewModel>声明为公共。否则，无论哪一个调用该活动，都无法将其输入绑定到它。

其次，接收输入参数的不是您的_sequence。它是您必须调用和传递参数的动态活动，而不是序列。

最后，您正确地创建了DynamicActivityProperty，但在本例中，您不需要设置它的值。当您使用名为"Model"的输入调用Workflow.Invoker()时，相同的输入将被绑定到动态属性。

我刚刚编辑了你的代码，没有运行它。希望它能有所帮助！:)

public sealed class RuleSequenceAcitvity : NativeActivity<Sequence>
{
    private DynamicActivity _dynamicActivity;
    public InArgument<HomeIndexViewModel> Model { get; set; }

    protected override void Execute(NativeActivityContext context)
    {
        populateDynamicActivity();

        var input = new Dictionary<string, object>();

        // It was throwing a null reference because Model
        // was private, so the input that the activity was receiving 
        // was never binded to it.

        var model = context.GetValue<HomeIndexViewModel>(this.Model);
        input.Add("Model", model);

        // It's the dynamic activity that contains input arguments.
        // Not the sequence. 

        WorkflowInvoker.Invoke(_dynamicActivity, input);
    }

    private void populateDynamicActivity()
    {
        //get the list of rules from repository
        var rules = 
            ObjectFactory
            .Container
            .GetInstance<IRuleRepository>()
            .Rules
            .ToList();

        //Declare a dynamic property as the view model
        var inProperty = new DynamicActivityProperty
        {
            Name = "Model",
            Type = typeof(InArgument<HomeIndexViewModel>)
        };

        _dynamicActivity = new DynamicActivity() 
        { 
            Properties = { inProperty } 
        };

        //Import references
        Common.AddVbSetting(activity);

        var sequence = new Sequence();
        activity.Implementation = () => sequence

        //Sort Descending - those added first are lowest priority
        var sortedRules = rules.OrderBy(x => x.Priority).ToList();

        foreach (var inRule in rules)
        {
            var outRule = RuleConverter.ToIfActivity(inRule);
            sequence.Activities.Add(outRule);
        }

    }
}