File locked after encryption - vb.net

Question

I have a small app that is designed to go through a folder and encrypt all the files and delete the non-encrypted version. The encryption works correctly but when I go to delete the file it is locked. Once the app is closed the file is no longer locked. My code is
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim path As String = Directory.GetCurrentDirectory()
Dim parent As DirectoryInfo = Directory.GetParent(path)
Dim completions As String = parent.FullName & "\Attachments_Completions"
Dim di As New DirectoryInfo(completions)
Dim fi As FileInfo() = di.GetFiles()
Dim dra As FileInfo
For Each dra In fi
If dra.Name <> "Completions.txt" And dra.Name <> "Attachments.txt" Then
Dim tmpFileName As String = String.Format("{0}\qqzr_{1}", dra.DirectoryName, dra.Name)
Dim encryptedName As String = String.Format("{0}\{1}", dra.DirectoryName, dra.Name)
FileSystem.Rename(String.Format("{0}\{1}", dra.DirectoryName, dra.Name), String.Format("{0}\qqzr_{1}", dra.DirectoryName, dra.Name))
cryptFile(tmpFileName, encryptedName, False)
File.Delete(tmpFileName)
End if
Next
End Sub
Sub cryptFile(ByVal sInputFilename As String, ByVal sOutputFilename As String, ByVal switch As Boolean)
' * Used to Encrypt or Decrypt a file
' ***********************************
Dim sKey As String = "a2#R|+~"
Try
Dim DES As New DESCryptoServiceProvider()
DES.Key() = ASCIIEncoding.ASCII.GetBytes(sKey)
DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey)
'Read the input file into array
Dim fsInput As New FileStream(sInputFilename, FileMode.Open, FileAccess.Read)
Dim bytearrayinput(fsInput.Length - 1) As Byte
fsInput.Read(bytearrayinput, 0, bytearrayinput.Length)
'Define the crypto transformer
Dim cryptoTransform As ICryptoTransform
If switch Then
cryptoTransform = DES.CreateEncryptor()
Else
cryptoTransform = DES.CreateDecryptor
End If
'Create the encrypting streams
Dim fsEncrypted As New FileStream(sOutputFilename, FileMode.Create, FileAccess.Write)
Dim cryptostream As New CryptoStream(fsEncrypted, cryptoTransform, CryptoStreamMode.Write)
'Write the output file
cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length)
cryptostream.Close()
cryptostream.Dispose()
'Release the input file
fsInput.Close()
fsInput.Dispose()
'Release the output file
fsEncrypted.Close()
fsEncrypted.Dispose()
Catch ex As Exception
End Try
End Sub
End Class
Can anyone help?
Cheers
James

Answer 1

Just add this
Catch ex As Exception
Debug.Write(ex.Message)
End Try
...and see what happens...

Answer 2

Thanks for the responses.
I have managed to resolve the problem by adding File.SetAttributes(tmpFileName, FileAttributes.Normal) before the File.Delete command