Wss3

when i create workflow,and using deleteTask method: I got error occur with my workflow in wss3 site,
it said error occur in workflow:
the code that I use :

using System;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Collections;
using System.Drawing;
using System.Linq;
using System.Workflow.ComponentModel.Compiler;
using System.Workflow.ComponentModel.Serialization;
using System.Workflow.ComponentModel;
using System.Workflow.ComponentModel.Design;
using System.Workflow.Runtime;
using System.Workflow.Activities;
using System.Workflow.Activities.Rules;
using System.Windows.Forms;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Workflow;
using Microsoft.SharePoint.WorkflowActions;


namespace deleted
{
    public sealed partial class Workflow1 : SequentialWorkflowActivity
    {
        public Workflow1()
        {
            InitializeComponent();
        }

        public Guid workflowId = default(System.Guid);
        public SPWorkflowActivationProperties workflowProperties = new SPWorkflowActivationProperties();

        private void deleteTask1_MethodInvoking(object sender, EventArgs e)
           
        {
           

            if (workflowProperties.Item.Title.ToString() == "Dara")
            {
                workflowProperties.Item.Delete();

            }
            else
            {
                string title="Invent";

               

                title=workflowProperties.Item.Title.ToString();



            }

        }

        private void onWorkflowActivated1_Invoked(object sender, ExternalDataEventArgs e)
        {

        }
    }


       
   
}