Infinite fraction value in sql query column in c#

Question

I'm facing a problem which occurs when trying to get the results of this simple sql query in NET (c#):

select 1/3 as col from dual

OracleDataReader.GetValue(i) throws an exception:

Arithmetic operation resulted in an overflow.
at Oracle.DataAccess.Types.DecimalConv.GetDecimal(IntPtr numCtx)
at Oracle.DataAccess.Client.OracleDataReader.GetDecimal(Int32 i)
at Oracle.DataAccess.Client.OracleDataReader.GetValue(Int32 i)

I've discovered that this error occures when number precision goes over 28 digits, so this leads to error:

select round(1/3,29) as col from dual

but this won't

select round(1/3,28) as col from dual

Trying to treat column value in c# as Double gets error "Invalid cast"

Does anyone know any approach to avoid this situation except of ubiquitous rounding of number columns?

Answer 1

Since data type is decimal it must be precise. It's not possible to store 1/3 infinite fraction in a decimal type. In general Conversions from Single or Double to Decimal throw an OverflowException if the result of the conversion is not representable as a Decimal. Thus I need to either read this value as a double or, be sure it's a correct decimal.