private void addDisease_btn_Click(object sender, EventArgs e)
        {
            var disease = new Disease
            {
                disease = addDisease_txt.Text
            };

            DiseaseService ds = new DiseaseService();
            ds.addDisease(disease);

            fillCheckBoxList();
            addDisease_txt.Clear();
        }
 private void fillCheckBoxList()
 {
     DiseaseService diseasesrvc = new DiseaseService();
     var list = diseasesrvc.getAllDiseases();
     disease_checklist.DataSource = list;
     disease_checklist.ClearSelected();
 }