WF.xoml：

<SequentialWorkflowActivity

  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/workflow"

  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

  x:Class="WorkflowConsoleApplication1.Workflow1"

  >

  <CodeActivity ExecuteCode="SayHello" />

  <x:Code>

    <![CDATA[ 

    private void SayHello(object sender, EventArgs e)

    {

      Console.WriteLine("Hello, workflow!");

    }

    ]]>

  </x:Code>

</SequentialWorkflowActivity>

HOST：

using(WorkflowRuntime workflowRuntime = new WorkflowRuntime())
            {
                AutoResetEvent waitHandle = new AutoResetEvent(false);
                workflowRuntime.WorkflowCompleted += delegate(object sender, WorkflowCompletedEventArgs e) {waitHandle.Set();};
                workflowRuntime.WorkflowTerminated += delegate(object sender, WorkflowTerminatedEventArgs e)
                {
                    Console.WriteLine(e.Exception.Message);
                    waitHandle.Set();
                };

                XmlReader xml = XmlReader.Create(@"F:\wf.xoml");
                WorkflowInstance instance = workflowRuntime.CreateWorkflow(xml);

                instance.Start();

                waitHandle.WaitOne();
            }

运行时报“验证失败”的错误，怎么回事？