[英]An exception of type 'System.Data.OleDb.OleDbException' occurred in System.Data.dll but was not handled in user code
[英]System.Data.OleDb.OleDbException' occurred in System.Data.dll
我應該能夠在文本框中輸入郵政編碼,因此程序運行時,應該在另一個文本框中輸入具有匹配郵政編碼的街道名稱。
但是,我收到此錯誤,但我無法真正解決。 錯誤出現在此行:
leesAdres = Adres.ExecuteReader();
整個代碼:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.OleDb;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace WindowsFormsApplication12
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void btnZoek_Click(object sender, EventArgs e)
{
OleDbConnection con = new OleDbConnection();
OleDbCommand Adres = new OleDbCommand("Select `street` from `postcode` where `postcode` LIKE txtPostcode.Text", con);
OleDbDataReader readAdres;
con.ConnectionString = "provider=Microsoft.Ace.OLEDB.12.0; data Source = C:\\Users\\name\\Documents\\school\\Adodotnet\\postcode.accdb";
con.Open();
readAdres = Adres.ExecuteReader();
while (leesAdres.Read())
{
txtStreet.Text = leesAdres.GetValue(0).ToString();
}
}
}
}
我懷疑這可能是我的SQL命令,但是我不確定,我沒有使用SQL和數據庫的經驗。
您錯誤地構造了查詢字符串
"Select `street` from `postcode` where `postcode` LIKE txtPostcode.Text", con
它應該是
"Select `street` from `postcode` where `postcode` LIKE '%" + txtPostcode.Text+ "%'" , con
為了使您的代碼更健壯並防止SQL注入,您可以采用以下形式構造它
SqlCommand cmd = new SqlCommand("Select `street` from `postcode` where `postcode` LIKE @P1" , conn);
cmd.Parameters.Add(P1);
cmd.Parameters["P1"].Value = txtTagNumber.Text;
還要研究使用stringbuilder類構造實際的字符串。
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