'Specified cast is not valid' in LAMBDA expression when querying float field

Question

I can not understand why "Specified cast is not valid exception" is thrown here:

c# code:

the exception throws when it reaches to m.HadapGoalPercent property, i tryed to change the datatype of x => x.Field<float>("HadapGoalPercent") also to single and double but its not working

 for (int i = 0; i < dt.Rows.Count; i++)
                    {
                        Sales.Month m = new Sales.Month(Yearnum, (byte)(i+1));
                        m.HadapGoal = dt.AsEnumerable().Where(x => x.Field<int>("MonthNum") == i + 1).Select(x => x.Field<int>("HadapGoalIncome")).Single();
                        m.ShotefGoal = dt.AsEnumerable().Where(x => x.Field<int>("MonthNum") == i + 1).Select(x => x.Field<int>("ShotefGoalIncome")).Single();
                        m.HadapGoalPercent = dt.AsEnumerable().Where(x => x.Field<int>("MonthNum") == i + 1).Select( x => x.Field<float>("HadapGoalPercent")).SingleOrDefault();
                        m.ShotefGoalPercent = dt.AsEnumerable().Where(x => x.Field<int>("MonthNum") == i + 1).Select(x => x.Field<float>("ShotefGoalPercent")).SingleOrDefault();
                        months.Add(m);
                    }

thats the definitions of ShotefGoalPercent and HadapGoalPercent properties inside Month Class:

 public Single ShotefGoalPercent { get; set; }
 public Single HadapGoalPercent { get; set; }

thats dt datatable:

(HadapGoalPercent and ShotefGoalPercent are defined as decimal(5,4) in sql database)

thank you very much for your time and considiration

Have you tried casting to decimal? After all, you said it's stored in the DB as a decimal. — sr28, Jul 27 '16 at 08:31
Take a look at `dt.Columns["HadapGoalPercent"].DataType` property. It should tell you what cast you need to use. — Ivan Stoev, Jul 27 '16 at 08:33
ok...thanks to @sr28 the problem was solved i have changed HadapGoalPercent , ShotefGoalPercent from single to decimal and the datatatpe in query to decimal also...its working. here is a thread i found now about the difference between decimal, float, single and double: http://stackoverflow.com/questions/618535/difference-between-decimal-float-and-double-in-net. why not write it as an answer? - thanks again — Jonathan Applebaum, Jul 27 '16 at 08:40

score 1 · Accepted Answer · answered Jul 27 '16 at 08:40

As per my comment I'm not sure why you aren't just casting as a decimal, as that's what you've stored it as in the DB. However, if you really want this as a double you can try:

Convert.ToDouble(value)

With the size of decimals you're passing in you should be fine. With very large decimals you run the risk of losing precision, but as I say, I don't think this will be an issue for you.

'Specified cast is not valid' in LAMBDA expression when querying float field

1 Answers1