Question

In our Oracle database, I have a table (say MYTABLE) with column VALUE_NUMBER of type NUMBER (NULL, no precision specified). This table contains a value 1178.2

When retrieving data from this column using standard ADO.Net (actually ODP.Net) and then converting the decimal value to a string, I get ‘1178.20’. Obviously, when converting the constant 1178.2M to a string, the output is 1178.2.

Digging deeper, I looked at the output of decimal.GetBits(), which turned out to be different, although when comparing both numbers they are really considered equal.

The code sample below illustrates the behaviour:

using (var connection = new OracleConnection("my connection string"))
{
    connection.Open();
    var command = connection.CreateCommand();
    command.CommandText = "SELECT VALUE_NUMBER FROM MYTABLE";
    command.CommandType = CommandType.Text;
    using (command)
    {
        var reader = command.ExecuteReader(CommandBehavior.Default);
        reader.Read();
        decimal oracleDecimal = reader.GetDecimal(reader.GetOrdinal("VALUE_NUMBER"));
        Console.WriteLine(oracleDecimal); // output: 1178.20 (NOT expected)
        var bitsFromOracle = decimal.GetBits(oracleDecimal).Select(x => x.ToString());
        var bitsFromOracleString = string.Join(",", bitsFromOracle.ToArray());
        Console.WriteLine(bitsFromOracleString); // 117820,0,0,131072

        // sanity check
        const decimal constantDecimal = 1178.2M;
        Console.WriteLine(constantDecimal); // output: 1178.2 (expected)
        var bitsFromConstant = decimal.GetBits(constantDecimal).Select(x => x.ToString());
        var bitsFromConstantString = string.Join(",", bitsFromConstant.ToArray());
        Console.WriteLine(bitsFromConstantString); // 11782,0,0,65536

        Console.WriteLine(oracleDecimal == constantDecimal); // True 
    }
}

How should this be explained?

Here’s the table CREATE & INSERT script to make this work:

CREATE TABLE MYTABLE (
  ID  NUMBER(10)             NOT NULL,
  VALUE_NUMBER           NUMBER
);

INSERT INTO MYTABLE(ID,VALUE_NUMBER) VALUES(1,1178.2);

UPDATE:

The answer by @Vash and his subsequent comment led to the right conclusion that the .Net decimal type actually contains information about it’s number of digits, even if they are irrelevant for equality. 1178.2M and 1178.20M have a different bit representation because of this, although obviously the .Equals() method and == operator consider these numbers equal.

Answer 1

The main problem you have is that you do not apply any format to row data that you recieve from data base.

If you want to have specific format you should specyfy it. In documentation you will find Formatting Types, there are all information how to deal with formatting.

If you just want to have result

Console.WriteLine(valueNumber.ToString("N1", CultureInfo.InvariantCulture));