將數據輸入文本框后如何自動顯示數據？ C＃

Question

我想當我輸入條碼號而不按任何按鈕時，數據會自動顯示，默認情況下數量為 1 我嘗試與txt_no相同，但它也需要按回車按鈕。

這是表格。 在此處輸入圖片說明

這是代碼：

 private void txtno_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 13)
            {




                txtqty.Enabled = true;
                txtqty.Focus();
            }
        }

        private void txtqty_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == 13)
            {
                try
                {
                    string txt="Select * from products where id = '"+txtno.Text+"'";
                    MySqlCommand cmd = new MySqlCommand(txt,con);
                    con.Open();
                    MySqlDataReader r = cmd.ExecuteReader();
                    while (r.Read())
                    {
                        int price = int.Parse(txtqty.Text.Trim()) * int.Parse(r[4].ToString());
                        totalprice = totalprice + price;


                        dataGridView1.Rows.Add(dataGridView1.RowCount, r[0], r[1], txtqty.Text.Trim(), r[4], price);
                    }
                    lbitems.Text = "" + (dataGridView1.RowCount - 1) + "";
                    lbtotal.Text = "" + totalprice + "";

                    con.Close();


                    }



                catch(Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error From Database");


                }
                txtno.Focus();
                txtno.Clear();

                txtqty.Enabled = false;
                txtqty.Clear();


            }

            }

Answer 1

您需要 txtno（即條形碼文本框）的TextChanged事件處理程序。
為 txtno 添加TextChanged事件處理程序，如下所示。

正如@HansKesting 所建議的，您應該清理輸入以避免 sql 注入。

    private void txtno_TextChanged(object sender, KeyPressEventArgs e)
    {       
        if(!string.IsNullOrEmpty(txtno.Text))
        {
            txtqty.Enabled = true;
            txtqty.Focus();

            Search();
        }
        else
        {
            txtqty.Enabled = false;     
        }
    }

    private void txtqty_KeyPress(object sender, KeyPressEventArgs e)
    {
        if (e.KeyChar == 13)
        {
            Search();
        }
    }

    private void Search()
    {
            try
            {
                string txt = "Select * from products where id = '" + txtno.Text + "'";
                MySqlCommand cmd = new MySqlCommand(txt, con);
                con.Open();
                MySqlDataReader r = cmd.ExecuteReader();
                while (r.Read())
                {
                    int price = int.Parse(txtqty.Text.Trim()) * int.Parse(r[4].ToString());
                    totalprice = totalprice + price;
                    dataGridView1.Rows.Add(dataGridView1.RowCount, r[0], r[1], txtqty.Text.Trim(), r[4], price);
                }

                lbitems.Text = "" + (dataGridView1.RowCount - 1) + "";
                lbtotal.Text = "" + totalprice + "";
                con.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Error From Database");
            }

            txtno.Focus();
            txtno.Clear();
            txtqty.Enabled = false;
            txtqty.Clear();
    }