'System.Data.OleDb.OleDbException'类型的未处理异常附加信息：条件表达式中的数据类型不匹配

I'm trying to get the price from a item in a combobox.Any ideas?

我试图从组合框中的项目中获得价格。任何想法?

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();**
        }
    }
 }

3 个解决方案

#1

It's not clear where you get the error. Next time try to be more explicit.

目前尚不清楚你在哪里得到错误。下次尝试更明确。

In the abobe code I see that you use string concatenation for building the sql statements. That is a bad practice due a sql injection and type missmatching.

在abobe代码中,我看到你使用字符串连接来构建sql语句。由于sql注入和类型不匹配,这是一种不好的做法。

Try to change

试着改变

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();
}

by this (I suspect the error is in the conversion of Cantitate -in a textBox- to a int or double -in database-):

通过这个(我怀疑错误是在Cantote的转换 - 在textBox-转换为int或双-in数据库 - ):

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();
}

#2

I understand that you are comparing a numerical field here. In that case you need to remove the single quotes in the sql query string.

我知道你在这里比较数字字段。在这种情况下,您需要删除sql查询字符串中的单引号。

#3

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

this was the problem, ty for the help guys hope i will be more clear next time.

这是问题所在,帮助人们希望下次我会更清楚。

#1