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合法性校验有很多方法，要视情况而定，比如说可以用正则表达式，如果是数字，除了正则表达式，也可以用诸如TryParse这种方法。
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这是我的简单串口代码：
Dim a As Integer
Dim b As Variant
Private Sub u_Click()
Text1.Text = "请先设置波特率与COM口！！！"
End Sub
Private Sub Cbo1_Click()
On Error GoTo blak '打开串口发生错误，提示信息
If MSComm1.PortOpen = True And a = 1 Then
MSComm1.PortOpen = False '必须先关闭端口，再对端口进行设置
MSComm1.CommPort = cbo1.ListIndex + 1 '端口号从0开始，必须加1
Else '有必要
MSComm1.CommPort = cbo1.ListIndex + 1
End If '注释的必须有，为第二次切换做准备，否则第二次换COM口会出问题
Exit Sub
blak:
MsgBox "串口不存在或被占用!", vbOKOnly, "提示信息" '必须是这种格式
End Sub
Private Sub Cbo2_Click() '单击事件，不是change事件
MSComm1.Settings = 1200 * 2 ^ cbo2.ListIndex "n,8,1" '设置端口的波特率，连接符前后必须空一格
End Sub
Private Sub cmd1_Click()
a = a + 1
If a = 1 Then
cmd1.Caption = "关闭串口"
cbo1.Enabled = False
MSComm1.PortOpen = True '打开串口
ElseIf a = 2 Then
cmd1.Caption = "打开串口"
cbo1.Enabled = True
MSComm1.PortOpen = False '关闭串口
a = 0
End If
End Sub
Private Sub cmd2_Click()
Text1.Text = "" '清空接收区
Text2.SetFocus
End Sub
Private Sub cmd3_Click()
Text2.Text = "" '清空发送区
Text2.SetFocus
End Sub
Private Sub cmd4_Click()
Dim d As Integer
Dim e(0) As Byte 'outbyte 输出字符
d = Val(Text2.Text)
e(0) = CByte(d)
MSComm1.OutBufferCount = 0 '清除发送缓冲区
MSComm1.Output = e '此命令执行一次发送8字节
End Sub
Private Sub Form_Load()
cbo1.ListIndex = 0
cbo2.ListIndex = 0
MSComm1.OutBufferCount = 0
MSComm1.InBufferCount = 0
End Sub
Private Sub MSComm1_OnComm()
Select Case MSComm1.CommEvent '返回最近的通信过程
Case comEvReceive '接受的数据
c: b = MSComm1.Input
If Option1.Value = True Then
Text3.Text = Text1.Text Hex(b(0)) '首次不行，因为有字符
Text1.Text = Text3.Text " " '转换一下
ElseIf Option2.Value = True Then
Text1.Text = Text1.Text b ""
End If
If MSComm1.InBufferCount 0 Then 'mscomm1.InBufferCount是缓冲区的数据数
GoTo c
End If
End Select
End Sub
Private Sub Option1_Click()
MSComm1.InputMode = comInputModeBinary '接收方式，十六进制
End Sub
Private Sub Option2_Click()
MSComm1.InputMode = comInputModeText '接收方式，字符格式
End Sub
Private Sub Text1_Change()
Text1.SelStart = Len(Text1.Text)
End Sub
将用户名，密码，用户类型存在数据库中，登陆时比较输入的值是否与数据库相同即可。
基础类库：
Imports Microsoft.VisualBasic
'执行Access语句的封装类。
Public Class AccessExecClass
Private conn As Data.OleDb.OleDbConnection
Private cmd As Data.OleDb.OleDbCommand
'创建类对象，并连接到数据库。
Sub New()
If openAccess Then
Else
msgbox("open Access Fail.")
End If
End Sub
'创建类对象，并连接到数据库。 '输入带目录名称的数据库文件名称：dbFileName，例如：“\DB数据库\企业数据库.aspx”
Sub New(ByVal dbFileName As String)
If OpenAccess(dbFileName) Then
Else
MsgBox("open Access Fail.")
End If
End Sub
Function OpenAccess() As Boolean
OpenAccess = False
'检验用户的帐号密码是否正确
Dim provider As String '= ConfigurationManager.ConnectionStrings("ConnectionString").ProviderName
provider = "Provider=Microsoft.Jet.OLEDB.4.0"
Dim database As String
database = "Data Source=" System.Web.HttpContext.Current.Server.MapPath("\数据库.aspx") ";Persist Security Info=true"
conn = New Data.OleDb.OleDbConnection(provider ";" database)
conn.Open()
OpenAccess = True
End Function
Function OpenAccess(ByVal dbFileName As String) As Boolean
OpenAccess = False
'检验用户的帐号密码是否正确
Dim provider As String '= ConfigurationManager.ConnectionStrings("ConnectionString").ProviderName
provider = "Provider=Microsoft.Jet.OLEDB.4.0"
Dim database As String
database = "Data Source=" System.Web.HttpContext.Current.Server.MapPath(dbFileName) ";Persist Security Info=true"
conn = New Data.OleDb.OleDbConnection(provider ";" database)
conn.Open()
OpenAccess = True
End Function
'关闭数据库。
Sub CloseAccess()
cmd = Nothing
conn.Close()
End Sub
'执行一条Access语句，执行成功就返回True。
Function ExecAccessString(ByVal AccessStr As String) As Boolean
cmd = New Data.OleDb.OleDbCommand(AccessStr, conn)
cmd.ExecuteNonQuery()
'Dim aa As Data.OleDb.OleDbDataReader = cmd.ExecuteReader
ExecAccessString = True
End Function
'返回读取到的数据，注意是用地址传递方式返回
Sub ExecAccessString(ByVal AccessStr As String, ByRef AccessReader As Data.OleDb.OleDbDataReader)
cmd = New Data.OleDb.OleDbCommand(AccessStr, conn)
cmd.ExecuteNonQuery()
AccessReader = cmd.ExecuteReader
End Sub
End Class
登陆代码：
Protected Sub LinkButton1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles LinkButton1.Click
Dim wl As New WebLog '用户登录记录开始，仅对购买了Log 功能的用户，才开放此功能，否则不会实际记录Log
Dim sql As String
Dim aDB As New AccessExecClass
Dim mypw As String
Label1.Visible = False
Label2.Visible = False
Label3.Visible = False
Label4.Visible = False
'没有输入时,不能进行登陆
If TextBox1.Text = "" Then
Label1.Visible = True
Return
End If
If TextBox2.Text = "" Then
Label2.Visible = True
Return
End If
If TextBox3.Text = "" Then
Label3.Visible = True
Return
End If
If TextBox3.Text = TextBox4.Text Then
Else
Label3.Visible = True
Return
End If
Dim iRnd As Integer = Rnd(10) * 100
TextBox3.Text = ""
TextBox4.Text = iRnd.ToString
'Dim iRnd As Integer = Rnd(10) * 100
'注意:此处需要加入防止注入分析,包含'的肯定是特别语句,讲拒绝.
If TextBox1.Text.IndexOf("'") 0 Or TextBox2.Text.IndexOf("'") 0 Then
TextBox1.Text = "不能输入非法字符,将强制清空"
TextBox2.Text = ""
Else
Dim pw As New MD5EnCode(13, 19) ' '2次加密
sql = "select 权限组号,ID , 密码 from 编辑人数据 where 编辑姓名='" + TextBox1.Text + "'"
Dim aa As Data.OleDb.OleDbDataReader '= cmd.ExecuteReader
aDB.ExecAccessString(sql, aa)
If aa.Read() Then
'密码正确()
'sql = aa(2)'需要特别注意：只能单向解密，不能直接转换
mypw = pw.simDeCode(pw.simDeCode(aa(2)))
If TextBox2.Text = mypw Then
Session("LOGIN_Name") = TextBox1.Text '设置登录后的用户名称
Session("Login_Group") = aa(0) 'cmd.ExecuteScalar '设置登录后的权限级别
Session("Login_ID") = aa(1) 'cmd.ToString
'cmd = Nothing
'conn.Close()
Call wl.NewLog("登录", "管理员成功登录")
Response.Redirect("../WebManages/Default.ASPX")
Else
'密码错误()
sql = sql.Replace("'", "【单引号】")
sql = sql.Replace(",", "【逗号】")
Call wl.NewLog("登录", "管理员失败的登录", TextBox1.Text, sql.Replace("""", "【双引号】"), "")
Label4.Visible = True
End If
Else
'密码错误()
sql = sql.Replace("'", "【单引号】")
sql = sql.Replace(",", "【逗号】")
Call wl.NewLog("登录", "管理员失败的登录", TextBox1.Text, sql.Replace("""", "【双引号】"), "")
Label4.Visible = True
End If
End If
End Sub