MySQL Casting in C#

Question

Okay, so I'm attempting to print out the contents of a table in a comma-separated file.

using (OdbcCommand com = new OdbcCommand("SELECT * FROM pie_data WHERE Pie_ID = ?", con)) {
    com.Parameters.AddWithValue("", Request.Form["pie_id"]);
    com.ExecuteNonQuery();
    using (OdbcDataReader reader = com.ExecuteReader()) {
        string finalstring = "";
        while (reader.Read()) {
            finalstring = reader.GetString(9) + ",";
            for (int i = 0; i <= 8; i = i + 1) {
                finalstring = finalstring + reader.GetString(i) + ",";
            }
        }
    }
    Response.Write(finalstring);
    noredirect = 1;
}

My table layout is:

CREATE TABLE `rent_data` (
`Pies` INT(10) UNSIGNED NOT NULL,
`Name` VARCHAR(85) NOT NULL,
`Email` VARCHAR(85) NOT NULL,
`Pie_Rent` DATE NOT NULL,
`Rent_To` DATE NOT NULL,
`Returned_Date` DATE NULL DEFAULT NULL,
`Place` VARCHAR(100) NOT NULL,
`Purpose` MEDIUMTEXT NOT NULL,
`Comments` MEDIUMTEXT NULL,
`Pie_ID` SMALLINT(5) UNSIGNED ZEROFILL NOT NULL,
INDEX `Pie_ID` (`Equipment_ID`)
)

The error I'm getting is this:

Exception Details: System.InvalidCastException: Unable to cast object of type 'System.Int64' to type 'System.String'.

On the line:

finalstring = finalstring + reader.GetString(i) + ",";

Answer 1

As it says here, conversions are done by the ODBC driver, and if they're not supported, GetString doesn't convert to string. Since you have non-string columns, you're facing this problem.

Instead of GetString, use GetValue, and then convert to string using ToString():

finalstring += reader.GetValue(i).ToString() + ",";