Storing .NET double value in Oracle DB - oracle

Question

I'm using ODP.NET to access Oracle DB from C# .NET.
Please see following code:
OracleConnection con = new OracleConnection();
con.ConnectionString = "User Id=user;Password=pass;Data Source=localhost/orcl";
con.Open();
/* create table */
DbCommand command = con.CreateCommand();
command.CommandType = CommandType.Text;
try
{
command.CommandText = "DROP TABLE TEST";
command.ExecuteNonQuery();
}
catch
{
}
//command.CommandText = "CREATE TABLE TEST (VALUE BINARY_DOUBLE)";
command.CommandText = "CREATE TABLE TEST (VALUE FLOAT(126))";
command.ExecuteNonQuery();
/* now insert something */
double val = 0.8414709848078965;
command.CommandText = "INSERT INTO TEST VALUES (" + val.ToString(System.Globalization.CultureInfo.InvariantCulture) + ")";
command.ExecuteNonQuery();
/* and now read inserted value */
command.CommandText = "SELECT * FROM TEST";
DbDataReader reader = command.ExecuteReader();
reader.Read();
double res = (double) (decimal)reader[0];
Console.WriteLine("Inserted " + val + " selected " + res);
The output from this is always:
Inserted 0,841470984807897 selected 0,841470984807897
But looking at variable values under debugger
val == 0.8414709848078965
res == 0,841470984807897
Why res is rounded up?
I looked into DB and there is stored rounded-up value.
On the other hand I used Oracle SQL Developer to modify this value, and I'm able to store 0.8414709848078965 in database?
I tried types NUMBER, FLOAT(126), BINARY_DOUBLE... always the same result.
Why there is a problem using ODP.NET?

Answer 1

OK, I have found that it works if parameter type is OracleDbType.BinaryDouble. But it causes my code to be dependent of ODP.NET. I wanted to use ADO.NET types (DbType) to achieve my code independency.

Answer 2

Oracle actually has a higher precision for it's numbers than .net!
I tried this in straight Oracle and it works fine, I recommend changing to use a param
e.g.
-- CREATE TABLE TEST (VALUE NUMBER(38,38)); (initial test)
INSERT INTO TEST VALUES (0.8414709848078965);
SELECT * FROM TEST;
VALUE
----------------------
0.8414709848078965
(recommendation)
OracleParameter param = cmd.CreateParameter();
param.ParameterName = "NUMBERVALUE";
param.Direction = ParameterDirection.Input;
param.OracleDbType = OracleDbType.Decimal;
param.Value = "0.8414709848078965";
command.Parameters.Add(param);