Object reference not set to an instance of an object

See more:

C#3.5

Hi guys

Am loading a dropdownlist...this the code behind aspx page

public void loadDDlClinicName()
        {
            if (!Page.IsPostBack)
            {
                systemBusinessLayer = new BusinessLayer();

                ArrayList clinicList = new ArrayList();
                clinicList = systemBusinessLayer.getClinics();

                ddlClinicName.DataSource = clinicList;
                ddlClinicName.DataTextField = "ClinicName";
                ddlClinicName.DataValueField = "ClinicRefNumber";
                ddlClinicName.DataBind();
                ddlClinicName.Items.Insert(0, ".:Select Clinic:.");
            }
        }

Now code in my BusinessLayer

public ArrayList getClinics()
        {
            using (SqlConnection con = new SqlConnection(ConnString))
            {
                SqlCommand cmd = new SqlCommand("procGetClinics", con);
                cmd.CommandType = CommandType.StoredProcedure;

                
                ArrayList clinicList = new ArrayList();

                try
                {
                    con.Open();
                    SqlDataReader read = cmd.ExecuteReader();
                    while (read.Read())
                    {
                        ClsClinic clinics = new ClsClinic(Convert.ToString(read["ClinicName"]), Convert.ToString(read["ClinicRefNr"]));
                        clinicList.Add(clinics);

                    }
                    read.Close();

                }
                catch (Exception exp)
                {
                    throw new ApplicationException(exp.Message);
                }

                return clinicList;
            }
        }

No i get the error saying "Object reference not set to an instance of an object."
in this line " ddlClinicName.DataSource = clinicList;" but i can see that the values are inside the "clinicList"