AES string encryption "Invalid IV block size" - encryption

Question

I am trying to encrypt a string using the code below. The issue is I get this error and I have no clue (I'm just learning about encryption) what to do or even where to look. The SharedKey and the IV have been supplied as Hex values. The SharedKey is 64 bytes and the IV is 32 bytes.
System.Security.Cryptography.CryptographicException: 'Specified initialization vector (IV) does not match the block size for this algorithm.'
Public Function Encrypt(ByVal strValue As String) As String
'Create instance of a Rijndael Managed object
Dim aes As New RijndaelManaged
'Set appropriate values of object
aes.Padding = PaddingMode.PKCS7
aes.KeySize = 256
aes.Mode = CipherMode.CBC
'Create streams to work with encryption process
Dim msEncrypt As New MemoryStream()
'SharedKey = "64 byte string"
'IV = "32 byte string"
Dim SharedKey As Byte() = Encoding.GetEncoding(1252).GetBytes(strSharedKey)
Dim IV As Byte() = Encoding.GetEncoding(1252).GetBytes(strIV)
Dim csEncrypt As New CryptoStream(msEncrypt, aes.CreateEncryptor(SharedKey, IV), CryptoStreamMode.Write)
'Convert string value to byte array
Dim toEncrypt As Byte() = Encoding.GetEncoding(1252).GetBytes(strValue)
toEncrypt = Encoding.Convert(Encoding.GetEncoding(1252), Encoding.UTF8, toEncrypt)
'Perform encryption
csEncrypt.Write(toEncrypt, 0, toEncrypt.Length)
csEncrypt.FlushFinalBlock()
'Return Base64 string
Return Convert.ToBase64String(msEncrypt.ToArray())
'Dim u As System.Text.UnicodeEncoding = System.Text.Encoding.Unicode
'Dim a As System.Text.ASCIIEncoding = System.Text.Encoding.ASCII
'Return a.GetByteCount(SharedKey) '64 bytes
End Function

Answer 1

For CBC mode (and most other modes) the IV length must be the same as the block length. By default with the .NET CLR RijndaelManaged cipher, the block length is 128 bits (16 bytes). You can set this with
aes.BlockSize = 256
Which would allow a 32 byte IV, but also use blocks of 32 bytes.
Also, your comments suggest that you are using a 64 byte (512 bit) key. That should be a 32 byte (256 bit) key.

Answer 2

These are what I used. Whether or not the returned value is correct, I have no idea yet.
Public Function Encrypt(ByVal strValue As String) As String
'Create instance of a Rijndael Managed object
Dim aes As New RijndaelManaged
'Set appropriate values of object
aes.Padding = PaddingMode.PKCS7
aes.KeySize = 256
aes.Mode = CipherMode.CBC
'Create streams to work with encryption process
Dim msEncrypt As New MemoryStream()
Dim SharedKey As Byte()
'SharedKey = ""
'IV = ""
SharedKey = StringToByteArray(strSharedKey)
Dim IV As Byte()
IV = StringToByteArray(strIV)
Dim csEncrypt As New CryptoStream(msEncrypt, aes.CreateEncryptor(SharedKey, IV), CryptoStreamMode.Write)
'Convert string value to byte array
Dim toEncrypt As Byte() = Encoding.GetEncoding(1252).GetBytes(strValue)
toEncrypt = Encoding.Convert(Encoding.GetEncoding(1252), Encoding.UTF8, toEncrypt)
'Perform encryption
csEncrypt.Write(toEncrypt, 0, toEncrypt.Length)
csEncrypt.FlushFinalBlock()
'Return Base64 string
Return Convert.ToBase64String(msEncrypt.ToArray())
End Function
Function StringToByteArray(text As String) As Byte()
Dim bytes As Byte() = New Byte(text.Length \ 2 - 1) {}
For i As Integer = 0 To text.Length - 1 Step 2
bytes(i \ 2) = Byte.Parse(text(i).ToString() & text(i + 1).ToString(), System.Globalization.NumberStyles.HexNumber)
Next
Return bytes
End Function
Any other ideas would be very helpful