Encrypt/Decrypt data in Vb.net and SQL Server - vb.net

Question

I currently use two functions, in a VB.net application, to encrypt/decrypt sensitive data (e.g. SSNs). I then store the encrypted data in a SQL Server database. Then, when reading data from SQL Server, the application decrypts it for display. This works just fine.
The problem with this solution is that it makes it impossible to write simple SQL queries that include those encrypted fields as the data that comes back is encrypted. I want to be able to run queries that return the data that was stored in encrypted format, in its original format (i.e. the actual, unencrypted data).
What is the best practice for accomplishing this? Should I not be using functions in the VB.net application, but rather using functions in SQL Server, for example? Or, do I need to create a DLL or something that has the two aforementioned functions that I then need to "install" somehow, so that they can be called from SQL Server? I am using SQL Server 2008 and Visual Studio 2017.
In case it's relevant, I have included the code for the functions.
Private key() As Byte = {}
Private IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF}
Public Function Decrypt(ByVal sStringToDecrypt As String, _
ByVal sEncryptionKey As String) As String
Dim inputByteArray(sStringToDecrypt.Length) As Byte
Try
key = System.Text.Encoding.UTF8.GetBytes(Left(sEncryptionKey, 8))
Dim des As New DESCryptoServiceProvider()
inputByteArray = Convert.FromBase64String(sStringToDecrypt)
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 ex As Exception
Return ex.Message
End Try
End Function
Public Function Encrypt(ByVal sStringToEncrypt As String, _
ByVal SEncryptionKey As String) As String
Try
key = System.Text.Encoding.UTF8.GetBytes(Left(SEncryptionKey, 8))
Dim des As New DESCryptoServiceProvider()
Dim inputByteArray() As Byte = Encoding.UTF8.GetBytes( _
sStringToEncrypt)
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.ToBase64String(ms.ToArray())
Catch ex As Exception
Return ex.Message
End Try
End Function