XceedBinaryEncodingLib.XceedBinaryEncoding encoder = new XceedBinaryEncodingLib.XceedBinaryEncodingClass(); 

encoder.License( @"your license key" );      

try
{
  encoder.EncodingFormat = new XceedBinaryEncodingLib.XceedBase64EncodingFormatClass(); 

  object source = "This is the data to encode";

  // Encode the data
  object encodedData = encoder.Encode( ref source, true ); 

  // Decoded the data
  object decodedData = encoder.Decode( ref encodedData, true );

  MessageBox.Show( System.Text.Encoding.Unicode.GetString( ( byte[] )decodedData ) );
}
catch( System.Runtime.InteropServices.COMException except )
{
  MessageBox.Show( except.ToString() );
}