Exception throws .. in SqlParameter

public string InsertRetailer(Business.Retailers objRetailer)
        {
            string retInsertRet = string.Empty;
            try
            {
              
                using (SqlConnection conn = Connection.OpenConnection())
               {
                   
                   SqlCommand cmd = new SqlCommand();
                   cmd.CommandText = "INSERT_RETAILER";
                   cmd.CommandType = System.Data.CommandType.StoredProcedure;
                   cmd.Connection = conn;
                   SqlParameter[] sqlParams=new SqlParameter [8];

                   SqlParameter RetailerCode = new SqlParameter("@RetailerCode", objRetailer.RetailerCode);
                   RetailerCode.Direction = System.Data.ParameterDirection.Input;
                   RetailerCode.DbType = System.Data.DbType.String;
                   sqlParams[0] = RetailerCode;

                   SqlParameter RetailerName = new SqlParameter("@RetailerName", objRetailer.RetailerName);
                   RetailerName.Direction = System.Data.ParameterDirection.Input;
                   RetailerName.DbType = System.Data.DbType.String;
                   sqlParams[1] = RetailerName;

                   SqlParameter EVD_No = new SqlParameter("EVD_No", objRetailer.EVD_No);
                   EVD_No.Direction = System.Data.ParameterDirection.Input;
                   EVD_No.DbType = System.Data.DbType.String;
                   sqlParams[2] = EVD_No;

                   SqlParameter Address = new SqlParameter("@Address", objRetailer.Address);
                   Address.Direction = System.Data.ParameterDirection.Input;
                   Address.DbType = System.Data.DbType.String;
                   sqlParams[3] = Address;

                   SqlParameter OpeningBalance = new SqlParameter("@OpeningBalance", objRetailer.OpeningBalance);
                   OpeningBalance.Direction = System.Data.ParameterDirection.Input;
                   OpeningBalance.DbType = System.Data.DbType.Currency;
                   sqlParams[4] = OpeningBalance;

                   SqlParameter WorkingHours = new SqlParameter("@WorkingHours", objRetailer.WorkingHours);
                   WorkingHours.Direction = System.Data.ParameterDirection.Input;
                   WorkingHours.DbType = System.Data.DbType.Double;
                   sqlParams[5] = WorkingHours;

                   SqlParameter ContactPerson_Name = new SqlParameter("@ContactPerson_Name", objRetailer.ContactPerson_Name);
                   ContactPerson_Name.Direction = System.Data.ParameterDirection.Input;
                   ContactPerson_Name.DbType = System.Data.DbType.String;
                   sqlParams[6] = ContactPerson_Name;

                   SqlParameter ContactPerson_Phone = new SqlParameter("@ContactPerson_Phone", objRetailer.ContactPerson_Phone);
                   ContactPerson_Phone.Direction = System.Data.ParameterDirection.Input;
                   ContactPerson_Phone.DbType = System.Data.DbType.Double;
                   sqlParams[7] = ContactPerson_Phone;

cmd.Parameters.AddRange(sqlParams);
                   cmd.ExecuteNonQuery();
                   retInsertRet = Msg.Value.ToString();