I am using VS2005. I am trying to use the DPAPI through the ProtectedData Class to encypt passwords.

However, when I try the below example, I always get errors on the ProtectedData and DataProtectionScope. The error messages are:
The name 'ProtectedData' does not exist in the current context
The name 'DataProtectionScope' does not exist in the current context

What can I do to get this to work?

using System.Security.Cryptography;

class Program
{
static void Main(string[] args)
{
String plainText = "mypassword";
String entropyText = "mykey";
byte[] plainBytes = Encoding.Unicode.GetBytes(plainText);
byte[] entropyBytes = Encoding.Unicode.GetBytes(entropyText);

//Errors occur here.
byte[] encryptedBytes = ProtectedData.Protect(plainBytes, entropyBytes, DataProtectionScope.CurrentUser);
}
}

Thanks,

Jerry