help! i get an error when i run the program on reader
i want to select the last column of DateToday but i get an error on reader
connection.Open();
OleDbCommand efgh = new OleDbCommand();
efgh.Connection = connection;
efgh.CommandText = "SELECT LAST(DateToday) FROM SalesPerDay";
OleDbDataReader reader = efgh.ExecuteReader();
if (reader.Read())
{
//this part gives me IndexOutOfRangeException:
label2.Text = reader["DateToday"].ToString();
}
connection.Close();
Your problem is that when you perform a Last function you lose the column name in the SQL. so when you reference the column by name, in the code, the name doesn't exist hence the IndexOutOfRangeException
either name the column i.e.
SELECT LAST(DateToday) as DateToday
or switch to index referencing i.e.
reader[0]
also as you are only returning single value you could switch to a scalar get rather than a row get
label2.Text = efgh.ExecuteScalar().ToString();
Try to change your query by providing the alias name to your column as
SELECT LAST(DateToday) as DateToday FROM SalesPerDay
or else you can try to use
label2.Text = reader[0].ToString();
Expanding on the correct answers given by others, you could also try checking if your column exists in your query and has a value using syntax like this:
var colIndex = reader.GetOrdinal("DateToday");
if (colIndex >= 0 && !reader.IsDBNull(colIndex))
{
var date = reader.GetDateTime(colIndex).ToShortDateString();
label2.Text = date;
}
label2.Text = reader[0].ToString();