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

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

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

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

  // Encoded the data to file
  encoder.WriteFile( ref data, XceedBinaryEncodingLib.EXBFileProcessing.bfpEncode, true, 
                     @"c:\test\encoded.txt", false );

  object bytesRead = null; 

  // Decode the encoded data located in the file to memory.
  object decodedData = encoder.ReadFile( @"c:\test\encoded.txt" ,0,0,
              XceedBinaryEncodingLib.EXBFileProcessing.bfpDecode ,true, ref bytesRead ); 

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