Not accurately read numeric number with a DataReader from SQLite-CodePudding

I got a problem where I can't read the data from my database correctly.

To give you an example, I got the important value that is in the database 6.69879289850025E-06, but I read 6.0 (which is not accurate since it's suppose to be way smaller) in the C# program.

Something similar happen to ImportantValue2 where the value that is in the database is -0,000158976621370616 and in my C# program I get 0,0.

 public double ImportantValue1 { get; set; }
 public double ImportantValue2 { get; set; }
 public string Note { get; set; }


public MyObject(SQLiteDataReader reader)
        {
            ImportantValue1 = Convert.ToDouble(reader["important_value_1"]); //Value in the database is REAL
            ImportantValue2 = Convert.ToDouble(reader["important_value_2"]);//Value in the database is REAL
            Note = reader["note"].ToString(); //Value in the database is TEXT
        }

Update

And this is how I call it.

using (SQLiteConnection c = new SQLiteConnection(connection))
{
    c.Open();
    using (SQLiteCommand cmd = new SQLiteCommand(sqlCommand, c))
    {
        using (SQLiteDataReader reader = cmd.ExecuteReader())
        {
            if (reader.Read())
            {
                objectFromBD = new MyObject(reader);
            }
        }
    }
}

And the SQLite code

CREATE TABLE "table"(
    "id" INTEGER,
    "important_value_1" REAL NOT NULL,
    "important_value_2" REAL NOT NULL,
    "note" TEXT NOT NULL,
    
    PRIMARY KEY ("id" AUTOINCREMENT)
);

Thank you for your help!

CodePudding user response：

reader["important_value_1"] will return index which column exists in your SQL script instead of your expectation value.

reader["important_value_1"] will get the value of the specified column.

You can try to use reader["important_value_1"] in reader.GetDouble function to read your data from columns.

ImportantValue1  = reader.GetDouble(reader["important_value_1"])
ImportantValue2  = reader.GetDouble(reader["important_value_2"])

SqliteDataReader.Item[] Property

Note

You might need to use reader.Read() let the reader point to read the next row if you want.

while (reader.Read()){
   //... read all rows from your db
}

CodePudding user response：

Here is a temporary solution I got, but that is not efficient.

I saw that I can read a string with the reader, but I couldn't do it with a double. So I used reader.GetString(rowValue); and than I converted the string to a double using the fonction below.

public double StringToDoubleWithNotation(string value)
{
    return Convert.ToDouble(Decimal.Parse(value, NumberStyles.AllowExponent | NumberStyles.AllowDecimalPoint));
}

Now everything is fine, but I would prefer to see a better solution since doing 3 conversion is not that efficient.