A More Robust Approach for Handling XName Objects in LINQ to XML

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One of the advantages of V2 of the Open XML SDK is that it provides us with a strongly typed XML document object model (DOM).  Because elements are represented by classes, and attributes are represented by properties in the classes, developers are not at risk of misspelling element and attribute names.  I was chatting about the Open XML SDK V2 with a customer, who appreciated the advantages of this approach.  However, V2 of the SDK is not an option for them, because it won’t be available to use to build a shipping product until the release of the next version of Office, and this doesn’t fit their schedule.  There is another approach using V1 of the SDK and LINQ to XML that provides some of the benefits of a strongly typed DOM.  The approach consists of declaring a static class with static, initialized XName and XNamespace fields in the class, and then using those XName and XNamespace objects in the LINQ to XML code to create and query XML trees.

By using an approach of automatically generating (from XSD) the static classes that contain the names, it assures that the names and namespaces are not misspelled.  In addition, this approach has the benefit of pre-atomization of the XName and XNamespace objects.  I’ve written a few posts on the benefits of pre-atomization of XName and XNamespace objects:

Writing Robust LINQ to XML Code that Performs Well

Atomized XName and XNamespace Objects

Preatomization of XName Objects

Pre-atomization can yield performance benefits both when creating and querying XML trees.  The static members of the class are initialized at application startup time.  After startup, the application will not need to further atomize any XName or XNamespace objects.

There is one additional advantage – you get some level of Intellisense support when you use this approach.

The Open XML Markup has a fair number of element and attribute names – I don’t know the exact count.  As a data point, I queried a quite large Open XML document for distinct element and attribute names (the Ecma Open XML Specification Part 4), and counted 809 distinct qualified names in 21 namespaces.

I wondered if pre-atomization of two or three thousand XName objects would present a performance problem on application startup, so I wrote a small program to generate a program that contains 3800 initialized XName objects.  I took care to generate names that are representative of the names in the Open XML specification – some are short, some are long, and the names are in a variety of namespaces.  When run on a fairly slow laptop (2 ghz, 1 core), the program initialization took approximately 1/2 of a second, which is reasonable.  Further on in this post, I present the small program that generates the test program.

The following example shows the approach of declaring a couple of static classes that contains static initialized fields.  You can see that code in Main uses the initialized names in the static classes both for the construction of the XML tree, and in a query:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
 
publicstaticclassPkg
{
    publicstaticXNamespace ns_pkg =
        "http://schemas.microsoft.com/office/2006/xmlPackage";
 
    publicstaticXName package = ns_pkg + "package";
    publicstaticXName part = ns_pkg + "part";
    publicstaticXName name = ns_pkg + "name";
    publicstaticXName contentType = ns_pkg + "contentType";
    publicstaticXName xmlData = ns_pkg + "xmlData";
}
 
publicstaticclassExt
{
    publicstaticXNamespace ns_ext =
        "http://schemas.openxmlformats.org/officeDocument/2006/extended-properties";
 
    publicstaticXName Properties = ns_ext + "Properties";
    publicstaticXName Template = ns_ext + "Template";
    publicstaticXName TotalTime = ns_ext + "TotalTime";
}
 
classProgram
{
    staticvoid Main(string[] args)
    {
        var pkg = newXElement(Pkg.package,
            newXAttribute(XNamespace.Xmlns + "pkg",
                "http://schemas.microsoft.com/office/2006/xmlPackage"),
            newXElement(Pkg.part,
                newXAttribute(Pkg.name, "/docProps/app.xml"),
                newXAttribute(Pkg.contentType,
                    "application/vnd.openxmlformats-officedocument.extended-properties+xml"),
                newXElement(Pkg.xmlData,
                    newXElement(Ext.Properties,
                        newXAttribute("xmlns", Ext.ns_ext),
                        newXElement(Ext.Template, "Normal.dotm"),
                        newXElement(Ext.TotalTime, "1")
                    )
                )
            )
        );
 
        var totalTime =
            (from e in pkg.Descendants(Ext.TotalTime)
             select (int)e)
            .First();
 
        Console.WriteLine(totalTime);
    }
}
 

Here is the program that generates the test program:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
 
classProgram
{
    staticHashSet<string> usedNames;
 
    staticvoid Gen(string className, string nsAbbr, string ns, int count)
    {
        Console.WriteLine("public static class {0}", className);
        Console.WriteLine("{");
        Console.WriteLine("    public static XNamespace {0} = \"{1}\";", nsAbbr, ns);
        Console.WriteLine();
       
        Random r = newRandom();
 
        for (int i = 0; i < count; i++)
        {
            string s = "";
            // the following loop (using the usedNames HashSet) makes sure that
            // the code does not generate duplicate names.
            while (true)
            {
                // make sure that the first character of the name is a letter A-Z
                char startChar = (char)('A' + (int)(r.NextDouble() * 26));
                Guid g = Guid.NewGuid();
                int len = (int)Math.Floor(r.NextDouble() * 12 + 2);
                s = startChar.ToString() +
                    g.ToString()
                     .Replace("-", "")
                     .Substring(0, len);
 
                if (usedNames.Add(s))
                    break;
            }
            Console.WriteLine("    public static XName {0} = {1} + \"{0}\";", s, nsAbbr);
        }
        Console.WriteLine("}");
        Console.WriteLine();
    }
 
    staticvoid Main(string[] args)
    {
        Console.WriteLine(@"using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
");
        usedNames = newHashSet<string>();
        Gen("Ns_W", "ns_w",
            "schemas.openxmlformats.org/wordprocessingml/2006/main", 1000);
        Gen("Ns_VE", "ns_ve",
            "http://schemas.openxmlformats.org/markup-compatibility/2006", 200);
        Gen("Ns_O", "ns_o",
            "urn:schemas-microsoft-com:office:office", 1000);
        Gen("Ns_R", "ns_r",
            "http://schemas.openxmlformats.org/officeDocument/2006/relationships", 600);
        Gen("Ns_M", "ns_m",
            "http://schemas.openxmlformats.org/officeDocument/2006/math", 1000);
        Console.WriteLine(@"
public class Program
{
    public static void Main(string[] args)
    {
        Console.WriteLine(""Entered Main"");
    }
}
");
    }
}
 

The test program looks something like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
 
publicstaticclassNs_W
{
    publicstaticXNamespace ns_w = "schemas.openxmlformats.org/wordprocessingml/2006/main";
 
    publicstaticXName A2dff9d51ac4 = ns_w + "A2dff9d51ac4";
    publicstaticXName F362d21f0a = ns_w + "F362d21f0a";
    publicstaticXName Ne594dbac67 = ns_w + "Ne594dbac67";
    publicstaticXName X4cad35 = ns_w + "X4cad35";
    publicstaticXName Ybca171196db = ns_w + "Ybca171196db";
    publicstaticXName C41d0325b2028 = ns_w + "C41d0325b2028";
    publicstaticXName D3e0eb73ab5a94 = ns_w + "D3e0eb73ab5a94";
    publicstaticXName M5df215a698c = ns_w + "M5df215a698c";
    publicstaticXName Zebe33a = ns_w + "Zebe33a";
    publicstaticXName J8d2563d1a13 = ns_w + "J8d2563d1a13";
    // ...
}
 
publicstaticclassNs_VE
{
    publicstaticXNamespace ns_ve = "http://schemas.openxmlformats.org/markup-compatibility/2006";
 
    publicstaticXName Afd026fa849e = ns_ve + "Afd026fa849e";
    publicstaticXName F206884417 = ns_ve + "F206884417";
    publicstaticXName N867bd48925 = ns_ve + "N867bd48925";
    publicstaticXName X801087 = ns_ve + "X801087";
    publicstaticXName Yf601615604c = ns_ve + "Yf601615604c";
    publicstaticXName C1701240984e3 = ns_ve + "C1701240984e3";
    // ...
}
 
publicstaticclassNs_O
{
    publicstaticXNamespace ns_o = "urn:schemas-microsoft-com:office:office";
 
    publicstaticXName A4a22d12b3d2 = ns_o + "A4a22d12b3d2";
    publicstaticXName Fa7d35e114 = ns_o + "Fa7d35e114";
    publicstaticXName N5154768163 = ns_o + "N5154768163";
    publicstaticXName Xdf110a = ns_o + "Xdf110a";
    publicstaticXName Yece0763cf81 = ns_o + "Yece0763cf81";
    publicstaticXName C5322c3f14297 = ns_o + "C5322c3f14297";
    publicstaticXName Dd1d69594fef44 = ns_o + "Dd1d69594fef44";
    publicstaticXName Mbfb32a08d32 = ns_o + "Mbfb32a08d32";
    publicstaticXName Z509498 = ns_o + "Z509498";
    publicstaticXName J16db47997f9 = ns_o + "J16db47997f9";
    // ...
}
 
publicstaticclassNs_R
{
    publicstaticXNamespace ns_r = "http://schemas.openxmlformats.org/officeDocument/2006/relationships";
 
    publicstaticXName A9676b45e848 = ns_r + "A9676b45e848";
    publicstaticXName F51ab6cb14 = ns_r + "F51ab6cb14";
    publicstaticXName Ncfb544f931 = ns_r + "Ncfb544f931";
    publicstaticXName X4f67fc = ns_r + "X4f67fc";
    // ...
}
 
publicstaticclassNs_M
{
    publicstaticXNamespace ns_m = "http://schemas.openxmlformats.org/officeDocument/2006/math";
 
    publicstaticXName A5993dd93a92 = ns_m + "A5993dd93a92";
    publicstaticXName Fa5592d4c1 = ns_m + "Fa5592d4c1";
    publicstaticXName N29869d8a94 = ns_m + "N29869d8a94";
    publicstaticXName Xb80c69 = ns_m + "Xb80c69";
    // ...
}
 
publicclassProgram
{
    publicstaticvoid Main(string[] args)
    {
        Console.WriteLine("Entered Main");
    }
}
 

Code is attached.