如何在NativeActivity中为孩子提供变量? [英] How do I make a variable available to children within a NativeActivity?

问题描述

我正在尝试为本地活动的孩子们提供一个特殊的财产.此本机活动是作为Beta 2的WF示例的一部分提供的ObjectContextScope的修改版本.我希望实例化的EF ObjectContext可用于ObjectContextScope实例子级.这是该活动的完整代码:

I'm attempting to make a particular property available to the children of a native activty. This native activity is a modified version of the ObjectContextScope that came as part of the WF samples for beta 2. I want the instantiated EF ObjectContext to be available to the ObjectContextScope instances children. Here is the complete code for the activity:

using System.Activities;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Data.Objects;
using System.Windows.Markup;
using System.Activities.Statements;

namespace Test.Data.Activities
{
	[ContentProperty("Body")]
	//[Designer(typeof(CMSContextScopeDesigner))]
	public class ObjectContextScope : NativeActivity
	{
		internal static string ObjectContextPropertyName = "_EF_ObjectContext";

		Variable<NoPersistHandle> noPersistHandle;
		Collection<Variable> variables;
		
		public ObjectContextScope()
			: base()
		{
			this.noPersistHandle = new Variable<NoPersistHandle>();
			this.ContextInstance = null;
		}

		public Collection<Variable> Variables
		{
			get
			{
				if (this.variables == null)
				{
					this.variables = new Collection<Variable>();
				}
				return this.variables;
			}
		}

		public Activity Body { get; set; }

		[RequiredArgument]
		[DefaultValue(null)]
		public InArgument<string> ConnectionString { get; set; }

		[RequiredArgument]
		public InArgument<string> ContainerName { get; set; }

		private Variable<ObjectContext> ContextInstance;

		protected override void CacheMetadata(NativeActivityMetadata metadata)
		{
			// child activities
			metadata.AddChild(this.Body);

			// arguments
			metadata.AddArgument(new RuntimeArgument("ConnectionString", typeof(string), ArgumentDirection.In, true));

			// variables
			metadata.AddImplementationVariable(this.noPersistHandle);
			metadata.AddImplementationVariable(this.ContextInstance);
			foreach (Variable variable in this.variables)
			{
				metadata.AddVariable(variable);
			}

			base.CacheMetadata(metadata);
		}

		protected override void Execute(NativeActivityContext context)
		{
			// enter a no persist scope
			NoPersistHandle noPersistHandle = this.noPersistHandle.Get(context);
			noPersistHandle.Enter(context);

			// get the connection string
			string connectionString = this.ConnectionString.Get(context);

			// get the context instance
			ObjectContext instance = this.ContextInstance.Get(context);

			// create the connection context
			instance = new ObjectContext(connectionString) { DefaultContainerName = this.ContainerName.Get(context) };

			// set the object context in the execution properties (to make it an ambient object context)
			context.Properties.Add(ObjectContextPropertyName, instance);

			// schedule the body activity
			context.ScheduleActivity(this.Body, new CompletionCallback(OnBodyComplete));
		}

		void OnBodyComplete(NativeActivityContext context, ActivityInstance completedActivity)
		{
			ObjectContext instance = this.ContextInstance.Get(context);

			if (instance != null)
			{
				instance.SaveChanges();
				instance.Dispose();
			}
		}
	}
}

子活动如何访问ContextInstance属性?谢谢！

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How do children activities access the ContextInstance property? Thanks!

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推荐答案

詹姆斯，

活动子类NativeActivity并通过

进行获取

Hi James,

Does making your activities subclass NativeActivity and get it by

var instance = (ObjectContext)context.Properties.Find(ObjectContextPropertyName)

还是您实际上是想让活动使用Variables/InArguments来访问它，以便您可以在内置活动中的一般表达式中使用它，例如IfActivity?

Tim

work?

Or do you actually want to have activities access it using Variables/InArguments instead, so that you can use it in general expressions in built-in activities e.g. IfActivity?

Tim

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