Not able to call events after unloading and loading of a workflow instance

protected void SendData_Click(object sender, EventArgs e)
        {
            Guid state_ID = Guid.NewGuid();
            Dictionary<string,> Params = new Dictionary<string,>();
            WorkflowInstance instance = null;
            StateMachineWorkflowInstance ins = null;
            SqlWorkflowPersistenceService sqlPersistenceService = new SqlWorkflowPersistenceService(ConfigurationManager.ConnectionStrings["PersistenceConnectionString"].ToString());

            WorkFlowDemo.states.state state = new WorkFlowDemo.states.state();
            ExternalDataExchangeService ExDateExchService = new ExternalDataExchangeService();
            WorkflowRuntime workflowRuntime = new WorkflowRuntime();
            workflowRuntime.AddService(sqlPersistenceService);
            workflowRuntime.AddService(ExDateExchService);
            //workflowRuntime.InstanceStore = store;
            ExDateExchService.AddService(state);
            instance =
                workflowRuntime.CreateWorkflow(typeof(Workflow1), Params, state_ID);
            Session["state_ID"] = state_ID;
            instance.Start();
            ins = new StateMachineWorkflowInstance(workflowRuntime, state_ID);
            state.SubmitContent(state_ID);

            if (ins.CurrentStateName == "Submitted")
            {
                SendData.Visible = false;
                Approve.Visible = true;
                Reject.Visible = true;
                Incomplete.Visible = true;
                Cancel.Visible = true;
            }
            instance.Unload();
        }

 protected void Approve_Click(object sender, EventArgs e)
        {
            Guid state_ID = Guid.NewGuid();
            Dictionary<string,> Params = new Dictionary<string,>();
            WorkflowInstance instance = null;
            StateMachineWorkflowInstance ins = null;
            SqlWorkflowPersistenceService sqlPersistenceService = new SqlWorkflowPersistenceService(ConfigurationManager.ConnectionStrings["PersistenceConnectionString"].ToString());


            //WorkFlowDemo.states.state state = new WorkFlowDemo.states.state();
            //ExternalDataExchangeService ExDateExchService = new ExternalDataExchangeService();
            //WorkflowRuntime workflowRuntime = new WorkflowRuntime();
            //workflowRuntime.AddService(sqlPersistenceService);
            //workflowRuntime.AddService(ExDateExchService);
            ////workflowRuntime.InstanceStore = store;
            //ExDateExchService.AddService(state);
            //instance =
            //    workflowRuntime.CreateWorkflow(typeof(Workflow1), Params, state_ID);

            
            WorkFlowDemo.states.state state = new WorkFlowDemo.states.state();
            ExternalDataExchangeService ExDateExchService = new ExternalDataExchangeService();
            WorkflowRuntime workflowRuntime = new WorkflowRuntime();
            workflowRuntime.AddService(sqlPersistenceService);
            workflowRuntime.AddService(ExDateExchService);
            Guid workflowId = new Guid(Session["state_ID"].ToString());
            //workflowRuntime.CurrentWorkflowInstanceID = workflowId;
            workflowRuntime.StartRuntime();

            if (workflowRuntime.IsStarted)
            {
                instance = workflowRuntime.GetWorkflow(workflowId);
            }
            instance.Load();
            //instance.ReloadTrackingProfiles();
            //workflowRuntime.AddService(ExDateExchService);
            state.Approved(state_ID);
            ins = new StateMachineWorkflowInstance(workflowRuntime, state_ID);

            if (ins.CurrentStateName == "Complete")
            {
                Data.Visible = true;
                Data.InnerText = "Approved";
                ContentTextBox.Visible = false;
                SendData.Visible = false;
                Approve.Visible = false;
                Reject.Visible = false;
                Incomplete.Visible = false;
                Cancel.Visible = false;
                if (workflowRuntime != null)
                {
                    workflowRuntime.StopRuntime();
                    workflowRuntime.Dispose();
                }
            }
        }

namespace WorkFlowDemo
{
   public class states
    {
       [Serializable]
       public class state: Istates,ISendDataService
       {
           private string getassigneddata;
           public event EventHandler<System.Workflow.Activities.ExternalDataEventArgs> submitted;
           public event EventHandler<System.Workflow.Activities.ExternalDataEventArgs> approved;
           public event EventHandler<System.Workflow.Activities.ExternalDataEventArgs> rejected;
           public event EventHandler<System.Workflow.Activities.ExternalDataEventArgs> completed;
           public event EventHandler<ReceivedDataEventArgs> ReceivedDataEvent;

           public void SubmitContent(Guid instanceID)
           {
               if (this.submitted != null)
               {
                  this.submitted(this, new System.Workflow.Activities.ExternalDataEventArgs(instanceID));
               }
           }

           public void Rejected(Guid instanceID)
           {
               if (this.rejected != null)
               {
                   this.rejected(this, new System.Workflow.Activities.ExternalDataEventArgs(instanceID));
               }
           }

           public void Approved(Guid instanceID)
           {
               if (this.approved != null)
                   this.approved(this, new System.Workflow.Activities.ExternalDataEventArgs(instanceID));
           }


}
}
}