Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.IO
Imports System.Xml
Imports System.Text
Imports System.Security.Cryptography

Partial Public Class EncryptToBaseDecryptFromBaseClass EncryptToBaseDecryptFromBase

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Public Shared Function EncryptToBaseString()Function EncryptToBaseString(ByVal stringToEncryptsql As SqlString, ByVal SEncryptionKeysql As SqlString) As SqlString
Dim stringToEncrypt As String = CType(stringToEncryptsql, String)
Dim SEncryptionKey As String = CType(SEncryptionKeysql, String)
Dim IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF}
Dim key() As Byte = {}
Try
key = System.Text.Encoding.UTF8.GetBytes(Left(SEncryptionKey, 8))
Dim des As New DESCryptoServiceProvider()
Dim inputByteArray() As Byte = Encoding.UTF8.GetBytes(stringToEncrypt)
Dim ms As New MemoryStream()
Dim cs As New CryptoStream(ms, des.CreateEncryptor(key, IV), CryptoStreamMode.Write)
cs.Write(inputByteArray, 0, inputByteArray.Length)
cs.FlushFinalBlock()
Return Convert.ToBaseString(ms.ToArray())
Catch e As Exception
Return CType(e.Message, SqlString)
End Try
End Function

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Public Shared Function DecryptFromBaseString()Function DecryptFromBaseString(ByVal stringToDecryptsql As SqlString, ByVal sEncryptionKeysql As SqlString) As SqlString
Dim stringToDecrypt As String = CType(stringToDecryptsql, String)
Dim sEncryptionKey As String = CType(sEncryptionKeysql, String)
Dim inputByteArray(stringToDecrypt.Length) As Byte
Dim IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF}
Dim key() As Byte = {}
Try
key = System.Text.Encoding.UTF8.GetBytes(Left(sEncryptionKey, 8))
Dim des As New DESCryptoServiceProvider()
inputByteArray = Convert.FromBaseString(stringToDecrypt)
Dim ms As New MemoryStream()
Dim cs As New CryptoStream(ms, des.CreateDecryptor(key, IV), CryptoStreamMode.Write)
cs.Write(inputByteArray, 0, inputByteArray.Length)
cs.FlushFinalBlock()
Dim encoding As System.Text.Encoding = System.Text.Encoding.UTF8
Return encoding.GetString(ms.ToArray())
Catch e As Exception
Return CType(e.Message, SqlString)
End Try
End Function

End Class

完成之后选择生成，部署即可

至于测试，是否可用，打开查询分析器，执行下面语句，
SELECT dbo.DecryptFromBaseString(dbo.EncryptToBaseString('123456','12345678'),'12345678')
如果出现正确的值：123456,说明成功了