这是我在第一个文本框中输入代码时查看所有下一个文本框和组合框的代码，但它显示了一些错误 [英] This is my code for view all the next text boxes and combobox when I entered a code in first text box but it shows some error

问题描述

  Imports  System.Data.OleDb 
 
 公共 类 workerdetails 
  Dim 提供程序作为 字符串 
  Dim  dataFile 作为 字符串 
  Dim  connString 作为 字符串 
 公共 myConnection 作为 OleDbConnection = 新 OleDbConnection 
 公共 dr  As  OleDbDataReader 
 私有  Sub  workerdetails_Load（ ByVal  sender  As  System。 Object ， ByVal  e  As  System.EventArgs）句柄  MyBase  .Load 
 provider =   Provider = Microsoft.ACE.OLEDB.12.0;数据源= 
 dataFile =   D：\ application \ accmasters.accdb  ' 将其更改为您的Access数据库位置 
 connString = provider& dataFile 
 myConnection.ConnectionString = connString 
 结束  Sub  
 
 私有  Sub  viewbutton_Click（发件人作为 对象，e  As  EventArgs） Handles  viewbutton .Click 
 myConnection.Open（）
 workername.Clear（）
 phno1.Clear（）
 phno2.Clear（）
 adharno.Clear（）
 address.Clear（）
 worktype.Text =   
  Dim  strt  As   String  
 strt =   SELECT * FROM workers WHERE（worker_code ='&a熔点; workercode.Text&  '） 
  Dim  cmd 作为 OleDbCommand = 新 OleDbCommand（strt，myConnection）
 dr = cmd.ExecuteReader 
  while  dr.Read（）
 workername.Text = dr（  worker_name）。ToString 
 phno1.Text = dr（  ph_no_1）。ToString 
 phno2.Text = dr（  ph_no_2）。ToString 
 adharno.Text = dr（  adhar_no）。ToString 
 address.Text = dr（  address）。ToString 
 worktype.Text = dr（  work_type）。ToString 
 结束  while  
 myConnection.Close（）
  End   Sub  
 结束 类 

我尝试了什么：



i在我的知识中尝试过最多但是它不起作用所以你能不能帮助我

解决方案

因为我们无法运行那些代码 - 我们没有你的数据 - 我们可以告诉你什么这是错误的，你并没有告诉我们它显示出一些错误实际上是什么。

但是......你需要改变一些事情。

首先，该代码对SQL注入是开放的，这意味着用户只需键入文本框就可以破坏或破坏您的数据库。永远不要连接字符串以形成SQL命令 - 总是使用参数化查询。

其次，不要使用 SELECT * FROM - 总是拼写出来您想要的列的名称。这样你就不会获取你不需要的数据，如果你犯了错误就可以很快得到错误。

第三，Command和Reader对象是稀缺资源，需要被处理当你完成它们时就正确了。

第四，当你只需要一行时为什么要循环？

所以试试：

 strt =   SELECT worker_name，ph_no_1，ph_no_2，adhar_no，address，work_type FROM workers WHERE worker_code = @WC 
 使用 cmd 作为 OleDbCommand = 新 OleDbCommand（strt，myConnection）
 cmd.Parameters.AddWithValue（  @WC，workercode.Text）
 使用 dr = cmd.ExecuteReader 
 如果 dr.Read（）
 workername.Text = dr（  worker_name）。ToString 
 phno1.Text = dr（  ph_no_1）。ToString 
 phno2.Text = dr（  ph_no_2）。ToString 
 adharno.Text = dr（  adhar_no）。ToString 
 address.Text = dr（  address ）。ToString 
 worktype.Text = dr（  work_type） .ToString 
 结束 如果 
 结束 使用 
 结束 使用 

Imports System.Data.OleDb

Public Class workerdetails
    Dim provider As String
    Dim dataFile As String
    Dim connString As String
    Public myConnection As OleDbConnection = New OleDbConnection
    Public dr As OleDbDataReader
    Private Sub workerdetails_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        provider = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source ="
        dataFile = "D:\application\accmasters.accdb" ' Change it to your Access Database location
        connString = provider & dataFile
        myConnection.ConnectionString = connString
    End Sub

    Private Sub viewbutton_Click(sender As Object, e As EventArgs) Handles viewbutton.Click
        myConnection.Open()
        workername.Clear()
        phno1.Clear()
        phno2.Clear()
        adharno.Clear()
        address.Clear()
        worktype.Text = ""
        Dim strt As String
        strt = "SELECT * FROM workers WHERE (worker_code= '" & workercode.Text & "')"
        Dim cmd As OleDbCommand = New OleDbCommand(strt, myConnection)
        dr = cmd.ExecuteReader
        While dr.Read()
            workername.Text = dr("worker_name").ToString
            phno1.Text = dr("ph_no_1").ToString
            phno2.Text = dr("ph_no_2").ToString
            adharno.Text = dr("adhar_no").ToString
            address.Text = dr("address").ToString
            worktype.Text = dr("work_type").ToString
        End While
        myConnection.Close()
    End Sub
End Class

What I have tried:

i tried most in my knowledge but it not work so could you please help me

解决方案

Since we can't run that code - we don't have your data - we can;t tell exactly what is wrong with it, and you don't tell us what "it shows some error" actually is.
But...there are a few things you need to change.
The first is that that code is wide open to SQL injection, which means that users can damage or destroy your database just by typing in text boxes. Never, ever concatenate strings to form an SQL command - always use parameterised queries.
Second, don't use SELECT * FROM - always spell out the names of the columns you want. That way you don;t fetch data you don;t need, and you can get an error sooner if you make a mistake.
Third, Command and Reader objects are scarce resources, and need to be Disposed correctly when you are finished with them.
Fourth, why are you looping when you only want one row?
So try:

strt = "SELECT worker_name, ph_no_1, ph_no_2, adhar_no, address, work_type FROM workers WHERE worker_code = @WC"
Using cmd As OleDbCommand = New OleDbCommand(strt, myConnection)
    cmd.Parameters.AddWithValue("@WC", workercode.Text)
    Using dr = cmd.ExecuteReader
        If dr.Read()
            workername.Text = dr("worker_name").ToString
            phno1.Text = dr("ph_no_1").ToString
            phno2.Text = dr("ph_no_2").ToString
            adharno.Text = dr("adhar_no").ToString
            address.Text = dr("address").ToString
            worktype.Text = dr("work_type").ToString
        End If
    End Using
End Using

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