Membership (Change password) Problem password default hashing

Hi 
I have a problem, i try to recreate the membership default password hashing.
 This is my code :
 
Private Function CreatePasswordHash(ByVal pass As String, ByVal salt As String) As String
Dim bytes As Byte() = Encoding.Unicode.GetBytes(pass)
Dim src As Byte() = Convert.FromBase64String(salt)
Dim dst As Byte() = New Byte(src.Length + bytes.Length) {}

System.Buffer.BlockCopy(src, 0, dst, 0, src.Length)
System.Buffer.BlockCopy(bytes, 0, dst, src.Length, bytes.Length)

Dim algorithm As HashAlgorit ...