Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

epeatedly in the same document. Whenever possible, applicationsshould use the namespace name rather than a prefix. The use of aprefix is more acceptable when only unique prefixes are used andpossibly only one namespace is defined in the document.Writing Encoded DataAs mentioned in the section "Methods of the XmlWriter Class," on page 141, the XMLtext writer object has two methods that write out XML data in a softly encrypted wayusing base64 and BinHex algorithms. The methods involved—WriteBase64 andWriteBinHex—have a rather straightforward interface. They simply take an array ofbytes and write it out starting at a specified offset and for the specified number of bytes.(As you saw in Chapter 2, XML reader classes have matching ReadBase64 andReadBinHex methods to comfortably read back encoded information.)Note In the .NET Framework, base64 encoding can also be performedthrough static methods exposed by the Convert class. In particular,the ToBase64String method takes an array of bytes and returns abase64-encoded string. Likewise, the FromBase64String methoddecodes a previously encoded string and returns it as an array ofbytes. For some reason, the .NET Framework does not providesimilar support for BinHex. BinHex, therefore, is supported onlythrough XML readers and writers.In the section "The XML Writer Programming Interface," on page 136, you learned howto serialize an array of strings to XML using the following array:string[] theArray = {"Rome", "New York", "Sydney","Stockholm", "Paris"};Let's look at how to write this array to a base64-encoded form. The structure of thecode we analyzed earlier does not need to be altered much. Only a couple of issuesneed to be addressed. The first concerns how strings are actually turned into an arrayof bytes. The second concerns the signature of the encoding methods. You can useWriteBinHex to write both element and attribute content in BinHex format, instead ofusing WriteBase64, as shown here:XmlTextWriter xmlw = new XmlTextWriter(filename, null);writer.Formatting = Formatting.Indented;writer.WriteStartDocument();writer.WriteComment("Array to Base64 XML");writer.WriteStartElement("array");writer.WriteAttributeString("xmlns", "x", null,"dinoe:isbn-0735618011");foreach(string s in theArray){writer.WriteStartElement("x", "element", null);writer.WriteBase64(Encoding.Unicode.GetBytes(s),0, s.Length*2);writer.WriteEndElement();133