从textbox1输入查询的值 按button1后查询，将结果从label2输出
Imports System.Data.OleDb
Public Class Form1
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
'定义一个baiOLEDB连接并实例化它
Dim con As New OleDbConnection
'定义一个OLEDB命令并实例化他
Dim cmd As New OleDbCommand
'定义一个OLEDBReader方法来读取数据库
Dim dr As OleDbDataReader
'初始化con的连接属性，使用OLEDB模式，数据源为：
con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=E:\字典项目\数据库\dic.mdb"
'打开OLEDB数据连接
con.Open()
'初始化OLEDB命令的连接属性为con
cmd.Connection = con
'初始化OLEDB命令的语句
cmd.CommandText = "select keyss from dic where ID=" & TextBox1.Text & ""
dr = cmd.ExecuteReader()
If dr.Read() Then
Label2.Text = dr(0)
End If
dr.Close()
con.Close()
End sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
End Class
运行查询的时候报错 “dr = cmd.ExecuteReader() 至少一个参数没有被指定值”
为什么啊
