Input string was not in a correct format (using SqlDataReader)

Question

I'm getting data from a remote Database, so I don't actually know the column types I'm dealing with. So I was using dataReader.GetString(X) as a default. I can save those values into variables, but when actually trying to send the variables into an object constructor it fails (before getting inside the constructor) with an error: System.FormatException: Input string was not in a correct format. If I can save them to string type variables why does it give an error when trying to use those variables to create an object and not before?

        //VARIABLES
        DateTime PreparationDate;
        string ClientId;
        string ClientName;
        string BL;
        string QTD_TOT;
        string QTD_PREP;
        string X_QTD;
        string TAXA;

            string query = GetPreparationsMACPAC;
            SqlConnection con = new SqlConnection(_connectionString);
            if (con.State == ConnectionState.Closed) con.Open();
            SqlCommand cmd = new SqlCommand(query, con);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlDataReader dr = cmd.ExecuteReader();

            List<PreparationViewModel> shippingsList = new List<PreparationViewModel>();

            PreparationViewModel prep = new PreparationViewModel(new DateTime(), "1", "2", "3", "4", "5", "6", "7");

            if (dr.HasRows)
            {
                while (dr.Read())
                {                    
                    PreparationDate = dr.GetDateTime(0);
                    ClientId = dr.GetString(1);
                    ClientName = dr.GetString(2);
                    BL = dr.GetString(3);
                    QTD_TOT = dr.GetString(4);
                    QTD_PREP = dr.GetString(5);
                    X_QTD = dr.GetString(6);
                    TAXA = dr.GetString(7);

                    //THE FOLLOWING OUTPUT IS CORRET (see below)
                    Console.WriteLine("{0},{1},{2},{3},{4},{5},{6},{7}", PreparationDate, ClientId, ClientName, BL, QTD_TOT, QTD_PREP, X_QTD, TAXA);

                    //FAILS HERE
                    try
                    {
                        prep = new PreparationViewModel(PreparationDate, ClientId, ClientName, BL, QTD_TOT, QTD_PREP, X_QTD, TAXA);
                    }
                    catch (Exception e)
                    {
                        Console.WriteLine(e);
                    }

                    shippingsList.Add(prep);
                }
            }

OUTPUT (1 Datetime + 7 Strings Seperated by ",")

09/04/2021 00:00:00,92843160002,RENAULT MONTAJE VALLADOLID,506653,120,120,0.000,1.0000000

CLASS MODEL

    public class PreparationViewModel
    {
        public PreparationViewModel()
        {

        }

        public PreparationViewModel(DateTime preparationDate, string clientId, string clientName, string transportDocumentId,
            string totalQuantity, string preparedQuantity, string xQuantity, string complianceRate)
        {
            //BREAKPOINT IS SET, NOT REACHED FROM THE TRY/CATCH CODE
            PreparationDate = preparationDate;
            ClientId = clientId;
            ClientName = clientName;
            TransportDocumentId = transportDocumentId;
            TotalQuantity = Int16.Parse(totalQuantity);
            PreparedQuantity = Int16.Parse(preparedQuantity);
            XQuantity = float.Parse(xQuantity);
            ComplianceRate = float.Parse(complianceRate);
        }

        public DateTime PreparationDate {get;set;}
        public string ClientId { get; set; }
        public string ClientName { get; set; }
        public string TransportDocumentId { get; set; }
        public int TotalQuantity { get; set; }
        public int PreparedQuantity { get; set; }
        public float XQuantity { get; set; }
        public float ComplianceRate { get; set; }
}

Answer 1

I'm getting data from a remote database so I don´t know exactly the column types

In that scenario, your best bet is probably something like:

short prepQty = Convert.ToInt16(reader.GetValue(5), CultureInfo.InvariantCulture);

(or if you don't want the invariant culture: replace with whatever culture you do want; if the values are strings and you don't know the culture: you've already lost the battle)

This will handle more data types and have better defined semantics when handling strings. It would be advisable to keep the read/parse code in the code that handles the reader, and have the PreparationViewModel just take the parsed value (the short ).