这是说你缺少引用一个程序
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就是说你项目用到了一些控件，但是你项目本身没有引用它
可以添加using
或者在页面最上面添加System, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=969db8053d3322ac
或者在你项目中BIN目录下右键添加引用
下面给你的列子
%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %
%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
Namespace="System.Web.UI" TagPrefix="asp" %
把程序集的那个DLL复制到程序的根目录，在“添加引用”的后面一栏就有显示具体路径
下面是完整的类，可以设置任意密码
'DES及md5加密解密----添加引用中添加对system.web的引用。
Imports System.Security.Cryptography
Imports System
Imports System.Text
Imports System.Web
''' summary
''' DES加密类
''' /summary
''' remarks/remarks
Public Class DESEncrypt
Public Sub DESEncrypt()
End Sub
Public Shared Function Encrypt(ByVal Text As String) As String
Return Encrypt(Text, "12345678")
End Function
Public Shared Function Encrypt(ByVal Text As String, ByVal sKey As String) As String
Dim des As New DESCryptoServiceProvider()
Dim inputByteArray As Byte()
inputByteArray = Encoding.Default.GetBytes(Text)
des.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8))
des.IV = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8))
Dim ms As New System.IO.MemoryStream()
Dim cs As New CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write)
cs.Write(inputByteArray, 0, inputByteArray.Length)
cs.FlushFinalBlock()
Dim ret As New StringBuilder()
Dim b As Byte
For Each b In ms.ToArray()
ret.AppendFormat("{0:X2}", b)
Next
Return ret.ToString()
End Function
Public Shared Function Decrypt(ByVal Text As String) As String
Return Decrypt(Text, "12345678")
End Function
Public Shared Function Decrypt(ByVal Text As String, ByVal sKey As String) As String
Dim des As New DESCryptoServiceProvider()
Dim len As Integer
len = Text.Length / 2
Dim inputByteArray(len - 1) As Byte
Dim x, i As Integer
For x = 0 To len - 1
i = Convert.ToInt32(Text.Substring(x * 2, 2), 16)
inputByteArray(x) = CType(i, Byte)
Next
des.Key = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8))
des.IV = ASCIIEncoding.ASCII.GetBytes(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8))
Dim ms As New System.IO.MemoryStream()
Dim cs As New CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write)
cs.Write(inputByteArray, 0, inputByteArray.Length)
cs.FlushFinalBlock()
Return Encoding.Default.GetString(ms.ToArray())
End Function
End Class
'以下是调用方法
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click '加密
Dim str_Encrypt As String = DESEncrypt.Encrypt("你要加密的文本，可以是任意长度", "密码，可以很长，如果省略这个参数就是默认的12345678")
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click '解密
Dim str_Decrypt As String = DESEncrypt.Decrypt("你要解密的文本, 可以是任意长度", "加密时用到的密码，如果省略这个参数就是默认的12345678")
End Sub
两种方法
1.
Shell(""Explorer.exe", AppWinStyle.NormalFocus")
2.
Dim proc As New Process
proc.StartInfo.FileName="Explorer.exe"
proc.Start
方法2给予更多的控制，如结束进程的方法Kill
