比较Windows窗体文本框输入值与数据库c# SQL中的值

本文关键字：数据库 SQL 比较 窗体 文本 输入 Windows | 更新日期: 2023-09-27 18:15:23

我希望比较windows窗体文本框上的输入到数据库中的字段。表格是"products"，字段是"ReOrderlevel"。如果输入到文本框中的值小于ReOrderlevel，我需要一个消息框来显示"Please Order Now"。我对c#完全陌生，不确定这些是否有意义，但我会把我的努力放在下面，以防有人能弄清楚我在做什么!提前谢谢你!

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
using System.Text.RegularExpressions;

namespace rescue_centre
{
public partial class FrmStock : Form
{
    public FrmStock()
    {
        InitializeComponent();
    }
    private void FrmStock_Load(object sender, EventArgs e)
    {
        refresh_data();
    }
    public void refresh_data()
    {
        string Query = "select * from stock";
        MySqlConnection mycon = new     MySqlConnection("datasource=localhost;username=root;password='';database=fsd;");            MySqlCommand cmd = new MySqlCommand(Query, mycon);
        MySqlDataAdapter adapter = new MySqlDataAdapter();
        MySqlDataReader Mdr;
        adapter.SelectCommand = cmd;
        DataTable dTable1 = new DataTable();
        adapter.Fill(dTable1);
        DtgStock.DataSource = dTable1;
        mycon.Open();
        Query = "Select * from stock";
        cmd = new MySqlCommand(Query, mycon);
        Mdr = cmd.ExecuteReader();
        CmbPrd.Items.Clear();
        while (Mdr.Read())
        {
            CmbPrd.Items.Add(Mdr.GetString("ProdCode"));
        }
        mycon.Close();
        mycon.Open();
        Query = "Select * from stock";
        cmd = new MySqlCommand(Query, mycon);
        Mdr = cmd.ExecuteReader();
        CmbLoc.Items.Clear();
        while (Mdr.Read())
        {
            CmbLoc.Items.Add(Mdr.GetString("LocCode"));
        }
        mycon.Close();
    }
   private void QtyTxt_Validating(object sender, CancelEventArgs e)
    {
        string query = "Select ReOrderlevel from Product where (ProdCode)='" + CmbPrd.Text + "';";
        MySqlConnection mycon = new MySqlConnection("datasource=localhost;username=root;password='';database=fsd");
        MySqlCommand cmd = new MySqlCommand(query, mycon);
        if
            QtyTxt.Text<ReOrderLevel
            MessageBox.Show("Stock Low Please Order Now")
        mycon.Open();
        cmd.ExecuteNonQuery();
        mycon.Close();
        refresh_data();

比较Windows窗体文本框输入值与数据库c# SQL中的值

需要在if语句之前执行查询。我将假设ReOrderlevel是一个整数，并且您的查询总是返回一行或多行。

MySqlCommand cmd = new MySqlCommand(query, mycon);
int ReOrderLevel = Convert.ToInt32(cmd.ExecuteScalar());
if(Convert.ToInt32(QtyTxt.Text) < ReOrderLevel)
{
    MessageBox.Show("Stock Low Please Order Now");
}

作为旁注，您不希望为Stock表查询数据库3次。在refresh_data方法上，在使用adapter.Fill(dTable1);之后，您可以像这样加载组合框:

CmbPrd.Items.Clear();
CmbLoc.Items.Clear();
foreach (DataRow row in dTable1.Rows)
{
   CmbPrd.Items.Add((string)row["ProdCode"]);
   CmbLoc.Items.Add((string)row["LocCode"]);
}

请使用参数化查询以避免SQL注入。代码示例

string query = "Select ReOrderlevel from Product where (ProdCode)= @prodcode;";
cmd.Parameters.AddWithValue("@prodcode", CmbPrd.Text);
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