Question

i have a problem, i tried this code :

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        conn.Open();
        OleDbCommand cmd = new OleDbCommand("UPDATE tbl_Fullname SET Firstname=@firstn,Lastname=@lastn,Middlename=@midn WHERE fnID=@idn", conn);

        cmd.Parameters.Add("@idn", OleDbType.VarChar).Value = textBox5.Text;
        cmd.Parameters.Add("@firstn", OleDbType.VarChar).Value = textBox1.Text;
        cmd.Parameters.Add("@lastn", OleDbType.VarChar).Value = textBox2.Text;
        cmd.Parameters.Add("@midn", OleDbType.VarChar).Value = textBox3.Text;
        cmd.ExecuteNonQuery();
        conn.Close();
    }

there was no error but when i ckecked my db access there is nothing changed.

is this the exact code for updatint and editing?

here is my whole code:

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {

    }

    private void button3_Click(object sender, RoutedEventArgs e)
    {

        OleDbCommand cmd = new OleDbCommand("INSERT INTO tbl_Fullname (Lastname,Firstname,Middlename) VALUES (@first,@last,@midn)",conn);

        conn.Open();
        cmd.Parameters.Add("@first", OleDbType.VarChar).Value = textBox1.Text;
        cmd.Parameters.Add("@last", OleDbType.VarChar).Value = textBox2.Text;
        cmd.Parameters.Add("@midn", OleDbType.VarChar).Value = textBox3.Text;
        cmd.ExecuteNonQuery();
        conn.Close();
    }

    private void textBox4_TextChanged(object sender, TextChangedEventArgs e)
    {
        conn.Open();
        OleDbCommand cmd2 = new OleDbCommand("SELECT fnID,Lastname,Firstname,Middlename FROM tbl_Fullname WHERE fnID= @id", conn);


        cmd2.Parameters.Add("@id", OleDbType.VarChar).Value = textBox4.Text;
        try
        {
            OleDbDataReader dr = cmd2.ExecuteReader();
            if (dr.Read())
            {
                textBox1.Text = dr[1].ToString();
                textBox2.Text = dr[2].ToString();
                textBox3.Text = dr[3].ToString();
                textBox5.Text = dr[0].ToString();

            }
            else
            {
                MessageBox.Show("No result");
            }

        }
        catch (Exception ex)
        {


            MessageBox.Show(ex.Message);
        }
        conn.Close();

    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        conn.Open();
        OleDbCommand cmd = new OleDbCommand("UPDATE tbl_Fullname SET Firstname=@firstn,Lastname=@lastn,Middlename=@midn WHERE fnID=@idn", conn);

        cmd.Parameters.Add("@idn", OleDbType.VarChar).Value = textBox5.Text;
        cmd.Parameters.Add("@firstn", OleDbType.VarChar).Value = textBox1.Text;
        cmd.Parameters.Add("@lastn", OleDbType.VarChar).Value = textBox2.Text;
        cmd.Parameters.Add("@midn", OleDbType.VarChar).Value = textBox3.Text;
        cmd.ExecuteNonQuery();
        conn.Close();
    }
}

}

i hope someone can help me. i need it badly. thank you in advance.

Answer 1

MSDN says:

The OLE DB .NET Provider does not support named parameters for passing parameters to an SQL statement or a stored procedure called by an OleDbCommand when CommandType is set to Text. In this case, the question mark (?) placeholder must be used. For example:

SELECT * FROM Customers WHERE CustomerID = ?

Therefore, the order in which OleDbParameter objects are added to the OleDbParameterCollection must directly correspond to the position of the question mark placeholder for the parameter in the command text.

So make it that way:

 private void button1_Click(object sender, RoutedEventArgs e)
    {
        conn.Open();
        OleDbCommand cmd = new OleDbCommand("UPDATE tbl_Fullname SET Firstname=?,Lastname=?,Middlename=? WHERE fnID=?", conn);

        cmd.Parameters.Add("@firstn", OleDbType.VarChar).Value = textBox1.Text;
        cmd.Parameters.Add("@lastn", OleDbType.VarChar).Value = textBox2.Text;
        cmd.Parameters.Add("@midn", OleDbType.VarChar).Value = textBox3.Text;
        cmd.Parameters.Add("@idn", OleDbType.VarChar).Value = textBox5.Text;
        cmd.ExecuteNonQuery();
        conn.Close();
    }

Note that order of parameters is important here!