VS 2015 - Decrypt String Stored As A Char

I have the following string stored in a char column of sql server (there are several this one is just an example):

Code:
ROix5LkY0Zps4MPcWnSmiw==

I also have the key used to generate the string:

Code:
6B9245B1A88A82FC328C8A1B8870E34D

And I found the following solution to decryp and encrypt:

Code:
Dim des As New TripleDESCryptoServiceProvider
Dim md5 As New MD5CryptoServiceProvider
'hash function
Function md5hash(value As String) As Byte()
Return md5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(value))
End Function

[Code] ...

It works like a charm when i encrypt and decrypt values set by me in the page;

But when i use the value stored in the DB it throws the following error;

"An exception of type 'System.Security.Cryptography.CryptographicException' occurred in mscorlib.dll but was not handled in user code

Additional information: Bad Data."

I am i using the wrong crypto class ? it's a length issue? the string is not base64?