Question

I think nothing’s wrong with the connection because when I open it, it does not throw any error. So I guess the error is when I’m executing a command. This is my code:

OleDbCommand cmd = new OleDbCommand("SELECT * FROM cars", conn);
cmd.CommandType = CommandType.Text;
int numbers = cmd.ExecuteNonQuery();

I tried using a message box to display the value of numbers but the result is always 0. The table cars contains 5 records. So why am I not getting the correct results?..

Answer 1

To the anonymous downvoter, the key part of the OP:

I tried using a message box to display the value of numbers but the
result is always 0. The table cars contains 5 records. So why am I not
getting the correct results?..

The OP is obviously trying to get a count of records in the table (a scalar aggregate) and not all of the table data.

My answer:

That’s because your query is returning a table and not a scalar value and you’re calling the incorrect function. Your query should be should be:

"SELECT COUNT(*) FROM cars"

And ExecuteNonQuery doesn’t actually expect any results to be returned. (You usually run insert, update and delete operations with ExecuteNonQuery.) You should be using ExecuteScalar which expects a single-valued result such as count(*).

All together now:

OleDbCommand cmd = new OleDbCommand("SELECT count(*) FROM cars", conn);
cmd.CommandType = CommandType.Text;
int numbers = cmd.ExecuteScalar();