Overflow error for encryption - vb.net

Question

I am getting an overflow error in the following code:
Public Shared Function AESFileEncrypt(inputFilename As String, outputFilename As String) As Boolean
'Create SymmetricAlgorithm object and specify the Key and IV.
Dim AES As RijndaelManaged = New RijndaelManaged
AES.Key = objKeys.aesKey
AES.IV = objKeys.aesIV
'Create an ICryptoTransform (Encryptor) object.
Dim Encryptor As ICryptoTransform
Encryptor = AES.CreateEncryptor
'Read the unencrypted file.
Dim InputFileStream As FileStream
InputFileStream = New FileStream(inputFilename, FileMode.Open, FileAccess.Read)
Dim InputFileData(CType(InputFileStream.Length, Integer)) As Byte
InputFileStream.Read(InputFileData, 0, CType(InputFileStream.Length, Integer))
Dim OutputFileStream As FileStream
OutputFileStream = New FileStream(outputFilename, FileMode.Create, FileAccess.Write)
'Create a CryptoStream object using the Stream and ICryptoTransform objects.
Dim EncryptCryptoStream As CryptoStream
EncryptCryptoStream = New CryptoStream(OutputFileStream, Encryptor, CryptoStreamMode.Write)
EncryptCryptoStream.Write(InputFileData, 0, InputFileData.Length)
EncryptCryptoStream.FlushFinalBlock()
'Clear any sensitive data from the cyptographic object.
AES.Clear()
'Close stream objects.
EncryptCryptoStream.Close()
InputFileStream.Close()
OutputFileStream.Close()
Return True
'Catch ex As Exception
'Debug.Print("AESFileEncrypt", ex.Message)
'Return False
'End Try
End Function
The error is at this line:
Dim InputFileData(CType(InputFileStream.Length, Integer)) As Byte
This happens on large files. I know it is because the byte array cannot be that large. Can I please have some help to modify this code to get it working?
Thanks
EDIT
This is my current work on this function:
Public Function AESFileEncrypt(inputFilename As String, outputFilename As String, Password As String, Salt As String) As Boolean
Dim AES As RijndaelManaged = New RijndaelManaged
Dim HashAlgorithm As String = "SHA1" 'Can be SHA1 or MD5
Dim PasswordIterations As String = 2
Dim InitialVector As String = "WinStorePassword" 'This should be a string of 16 ASCII characters.
Dim KeySize As Integer = 256 'Can be 128, 192, or 256.
Dim InitialVectorBytes As Byte() = Encoding.ASCII.GetBytes(InitialVector)
Dim SaltValueBytes As Byte() = Encoding.ASCII.GetBytes(Salt)
Dim DerivedPassword As PasswordDeriveBytes = New PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations)
Dim KeyBytes As Byte() = DerivedPassword.GetBytes(KeySize / 8)
Dim Encryptor As ICryptoTransform
Encryptor = AES.CreateEncryptor(KeyBytes, InitialVectorBytes)
Dim InputFileStream As FileStream
InputFileStream = New FileStream(inputFilename, FileMode.Open, FileAccess.Read)
Dim OutputFileStream As FileStream
OutputFileStream = New FileStream(outputFilename, FileMode.Create, FileAccess.Write)
Dim EncryptCryptoStream As CryptoStream
EncryptCryptoStream = New CryptoStream(OutputFileStream, Encryptor, CryptoStreamMode.Write)
Const BUFFER_SIZE As Integer = 4096
Dim buffer(BUFFER_SIZE - 1) As Byte
Dim Position As Long
Do
If (Position + BUFFER_SIZE) > InputFileStream.Length Then
InputFileStream.Read(buffer, Position, InputFileStream.Length - Position)
EncryptCryptoStream.Write(buffer, Position, BUFFER_SIZE)
Exit Do
Else
InputFileStream.Read(buffer, Position, BUFFER_SIZE)
EncryptCryptoStream.Write(buffer, Position, BUFFER_SIZE)
End If
Position += BUFFER_SIZE
Loop
EncryptCryptoStream.FlushFinalBlock()
AES.Clear()
EncryptCryptoStream.Close()
InputFileStream.Close()
OutputFileStream.Close()
Return True
End Function
Is this correct? I did a test an a small file, and the output was a lot larger than i expected?