Updating DB Data Else Insert?

[Untalented]

Hello,

I'm a fairly new programmer and trying to get some code working, that just doesn't want to work so came for some advice. Basically I'm having this search for a specific user_id. If it exists it should update the row. If it doesn't exist it should insert a new row with the appropriate data.

It appears to work for creating new rows. However, it never updates even if the row is there. I tested the update lines of code by itself and they work. So I'm doing something incorrectly. Take a look at the code below:

OleDbCommand cmd = new OleDbCommand("SELECT * FROM users WHERE user_id=?");
                cmd.Connection = con;
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.AddWithValue("user_id", userIDHiddenField.Value.ToString());
                using (OleDbDataReader Reader = cmd.ExecuteReader())
                {
                    if (Reader.HasRows)
                    {
                        Reader.Close();
                        cmd.CommandText = @"UPDATE users SET user_first_name = @user_first_name, " +
                                          "user_last_name = @user_last_name, user_email = @user_email " +
                                          "WHERE user_id = @user_id";
                        cmd.Connection = con;
                        cmd.CommandType = CommandType.Text;
                        cmd.Parameters.AddWithValue("@user_first_name", userFirstNameTextBox.Text);
                        cmd.Parameters.AddWithValue("@user_last_name", userLastNameTextBox.Text);
                        cmd.Parameters.AddWithValue("@user_email", userEMailTextBox.Text);
                        cmd.Parameters.AddWithValue("@user_id", userIDHiddenField.Value.ToString());
                        cmd.ExecuteNonQuery();
                    }
                    else
                    {
                        Reader.Close();
                        cmd.CommandText = @"INSERT INTO users (user_id, user_first_name, user_last_name, user_email) " +
                                          "VALUES (@user_id, @user_first_name, @user_last_name, @user_email)";
                        cmd.Connection = con;
                        cmd.CommandType = CommandType.Text;
                        cmd.Parameters.AddWithValue("@user_first_name", userFirstNameTextBox.Text);
                        cmd.Parameters.AddWithValue("@user_last_name", userLastNameTextBox.Text);
                        cmd.Parameters.AddWithValue("@user_email", userEMailTextBox.Text);
                        cmd.Parameters.AddWithValue("@user_id", userIDHiddenField.Value.ToString());
                        cmd.ExecuteNonQuery();
                    }
                }

Any help would be much appreciated.