protected void btnSearch_Click(object sender, EventArgs e)
        {
            EntityPatientDetails       objEntity = new EntityPatientDetails();
            BusinessViewPatientHistory objBus    = new BusinessViewPatientHistory();
            DataTable dt = new DataTable();

            if (ddlPatientId.SelectedIndex == 0)//PatientId not selected in DropDownList
            {
                objEntity.FirstName = ddlFirstName.SelectedItem.Text;
                objEntity.LastName  = ddlLastName.SelectedItem.Text;
                dt.Clear();
                dt = objBus.businessFillPatientHistoryUsingPatientName(objEntity);
            }
            else if (ddlFirstName.SelectedIndex == 0 && ddlLastName.SelectedIndex == 0)//Firsname and LastName not selected in DropDownList
            {
                objEntity.PatientId = Convert.ToInt32(ddlPatientId.SelectedItem.Text);
                dt.Clear();
                dt = objBus.businessFillPatientHistoryUsingPatientId(objEntity);
            }
            else
            {
                //Error massage: Eiter enter Patient Id or First Name and Lastname of the Patient whoes history you want to see.
            }
            gvViewPatientHistory.DataSource = dt;
            gvViewPatientHistory.DataBind();
        }
        public void fillPatientLastName()
        {
            BusinessViewPatientHistory bus = new BusinessViewPatientHistory();
            DataTable dt = bus.businessFillPatientLastName();

            ddlLastName.DataTextField  = dt.Columns[0].ToString(); //Patient Last Name
            ddlLastName.DataValueField = dt.Columns[0].ToString(); //Patient Last Name
            ddlLastName.DataSource     = dt;
            ddlLastName.DataBind();

            ListItem li = new ListItem("Select Patient\'s Last Name", "-1");

            ddlLastName.Items.Insert(0, li);
            //Inserted Listitem Index in ddlLastName control is [0]
            //But its valeu is -1
        }