System.Data.SqlClient stores wrong data in SQL Server

Question

I have a C# program pulling some data and put into SQL Server

public void UpdateElementInfo()
{
    var _db = new MyEntities();

    var mylist = _db.elements.Where(x => x.id != null);

    IList<ele> plist = mylist.ToList<ele>();

    foreach (ele p in plist)
    {
        var query = from myRow in dtrr.AsEnumerable()
                    where myRow.Field<string>("num") == p.id.ToString()
                    select myRow;
        var rrrr = query.OrderByDescending(x => x.Field<DateTime>("updated_at")).FirstOrDefault();

        {
            p.my_interested_param = (double?)rrrr.Field<decimal?>("parameter") * 100;

So if I do Console.WriteLine() this my_interested_param, it shows as expected, 4.12 for example. However, when I looked in SQL Server, this number is actually converted into 4.1200000000000003. Moreover, this conversion does not happen to all of the rows. So it is very strange to me.

I read that this might be due to the FLOAT data type chosen to store this number. However, what we could do if we have to use FLOAT to store it.

That's what happens with floating points. Why do you use it if you don't want this behaviour? — James Z, Oct 14 '17 at 19:56
I am using it because previous people used it. I do not want to touch the DB at this point, so I am thinking if there is solution on the C# coding level. Thanks. — superuserDoHaveStupidQ, Oct 14 '17 at 19:58
No, there is no solution. Floating points are not accurate numbers. See https://stackoverflow.com/questions/61872/use-float-or-decimal-for-accounting-application-dollar-amount — James Z, Oct 14 '17 at 20:00

System.Data.SqlClient stores wrong data in SQL Server

0 Answers0