InfoPath Dev

I have developed custom multilevel approval workflow. For the same i have taken following steps:

Project created:

1) ApprovalWorkflowFeature (Its contain content type fields _AprrovalStatus and _ApprovalNotes).

2)CustomApprovalForms (ApprovalForm.aspx)

3) Multilevel Approval Workflow (Business Logic).

Workflow get start when new item created into specific sharepoint library and it's show me In Process status. When i click on that it show me Task to do, click on assigned task title and its open ApprovalForm.aspx. When i press Approve button it invoke below method of CustomApprovalForms (ApprovalForm.aspx).

 protected void btnApprove_Click(object sender, EventArgs e)
    {
        Hashtable taskHash = new Hashtable();                               // Task data is sent via a Hash Table
        taskHash["_ApprovalNotes"] = txtApprovalNotes.Text;
        taskHash["_ApprovalStatus"] = true;

        SPWorkflowTask.AlterTask(this._TaskListItem, taskHash, true);       // Send the data to the task list, by altering the tasks value

        SPUtility.Redirect(this._TaskListAttachedTo.DefaultViewUrl,         // Redirect the UI back to the Task List.  You could chose
                            SPRedirectFlags.UseSource,
                            HttpContext.Current);
    }

and get aprroval status into Multilevel workflow by:

private void onApprovalTaskChanged_Invoked(object sender, ExternalDataEventArgs e)
        {
            // Get the Approval Status (Approved or Declined) from the Workflow Form
  this._primaryApprovalStatus = System.Convert.ToBoolean(onApprovalTaskChanged_AfterProperties1.ExtendedProperties["_ApporvalStatus"]);
        
            // Since the Approver notes field is a Text Field, we will need to get the value of the field
            // a bit differently.  We need to get the ID of the field first and then we can use the ID (GUID)
            // to get the fields value.  Some fields are stored in the Extended List by name and some by ID,
            // the safest way to get values is by using the ID, as I am showing you in ths step.
            Guid notesFieldID = workflowProperties.TaskList.Items[0].Fields["Approval Form Notes Field"].Id;

            // Check to see if the workflow is approved or not
            if (onApprovalTaskChanged_AfterProperties1.ExtendedProperties[notesFieldID] != null)
            {
                // Get the notes from the Approval Form
                _ApproverNotes = onApprovalTaskChanged_AfterProperties1.ExtendedProperties[notesFieldID].ToString();
            }

            // Set the Approval Task as completed
            this._primaryApprovalTaskCompleted = true;
        }