把数据加密后存入文件，之后对文件进行解密，解密后的文件长度好像变长了。

Question

'加密

Dim buffer() As Byte = {125, 56, 87, 125, 55, 87, 25, 45......}

Dim fs  As New IO.FileStream("C:\file.txt", IO.FileMode.Create, IO.FileAccess.Write, IO.FileShare.None)
Dim cs As New CryptoStream(fs, des.CreateEncryptor, CryptoStreamMode.Write)
cs.Write(buffer, 0, buffer.Length)
cs.Close()

'解密

fs = New IO.FileStream("C:\file.txt", IO.FileMode.Open)

cs = New CryptoStream(fs, des.CreateDecryptor, CryptoStreamMode.Read)
Dim buffer(fs.Length) As Byte
cs.Read(buffer, 0, fs.Length)
cs.Close()

这样加密/解密之后，发现解密后的字节数组长度比原来要长了，在最后多了一些“空”的数据？