類型'System.Data.OleDb.OleDbException'的未處理異常附加信息：條件表達式中的數據類型不匹配

Question

我正在嘗試從組合框中的項目中獲取價格。有什么想法嗎？

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 System.Data.OleDb;

namespace Aplicatie_proiect
{
    public partial class Form2 : Form

    {
        private OleDbConnection connection = new OleDbConnection();
        public Form2()
        {
            InitializeComponent();
            connection.ConnectionString =    @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\SleepyHitman-      V2\Documents\Inventory1.accdb;
    Persist Security Info=False;";
        }

        private void txt_order_Click(object sender, EventArgs e)
        {
            Double PT = new Double();
            connection.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            command.CommandText = "insert into Comenzi (Produs,Cantitate) values('"+txt_Produs.Text+"','"+txt_Cantitate.Text+"',)" ; //+ sa adaug useru care e logat din form 1
            command.ExecuteNonQuery();
            connection.Close();
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            connection.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            string query = "select * from Inventory";
            command.CommandText = query;
            OleDbDataReader reader = command.ExecuteReader();

            while (reader.Read())
            {
                txt_Produs.Items.Add(reader["Produs"].ToString());
            }
            connection.Close();

        }
        private void txt_Produs_SelectedIndexChanged(object sender, EventArgs e)
        {
            **connection.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = connection;
            string query = "select * from Inventory where Pret ='" + txt_Produs.Text + "'";
            command.CommandText = query;
            OleDbDataReader reader = command.ExecuteReader();

            while (reader.Read())
            {
                txt_Pret.Text = reader["Pret"].ToString();

            }
            connection.Close();**
        }
    }
 }

Answer 1

目前尚不清楚您在哪里得到錯誤。 下次嘗試更加明確。

在abobe代碼中，我看到您使用字符串連接來構建sql語句。 由於sql注入和類型不匹配，所以這是一種不好的做法。

嘗試改變

private void txt_order_Click(object sender, EventArgs e)
{
    Double PT = new Double();
    connection.Open();
    OleDbCommand command = new OleDbCommand();
    command.Connection = connection;
    command.CommandText = "insert into Comenzi (Produs,Cantitate) values('"+txt_Produs.Text+"','"+txt_Cantitate.Text+"',)" ; //+ sa adaug useru care e logat din form 1
    command.ExecuteNonQuery();
    connection.Close();
}

這樣（我懷疑錯誤是在Cantitate-在textBox-中轉換為int或double -in數據庫-中）：

private void txt_order_Click(object sender, EventArgs e)
{
    Double PT = new Double();
    connection.Open();
    OleDbCommand command = new OleDbCommand();
    command.Connection = connection;
    command.CommandText = "insert into Comenzi (Produs,Cantitate) values(@product, @cantitate)" ; //+ sa adaug useru care e logat din form 1
    command.Parameters.AddWithValue("@product", txt_Produs.Text);
    command.Parameters.AddWithValue("@cantitate", Convert.ToInt32(txt_Cantitate.Text);
    command.ExecuteNonQuery();
    connection.Close();
}

Answer 2

我了解到您正在此處比較數字字段。 在這種情況下，您需要刪除sql查詢字符串中的單引號。

Answer 3

string query = "select Pret from Inventory where Produs ='" + txt_Produs.Text + "'";

這就是問題所在，請幫忙的人希望下次我會更加清楚。