My first Sangeeth Sammelan concert

I just came back after my first sangeeth sammelan concert held in New Delhi on 3rd october at FICCI auditorium organised by All India Radio. It will be relayed on Channel A from 10pm to 11pm on 3rd Nov 2009. I accompanied T.M. Krishna on the violin and Poongulam Subramaniam was on the mridangam. The concert went on very well and the hall was packed. The list is

1. Neelayadakshi - Paras - Syama Sasthri
2. RTP - Begada - Adhi - Kailasapathe pasupathe umapathe namosthuthe
3. Javali in Kaanada

His begada rendition was truly awesome and very inspiring. I heard a lot of new phrases. Poongulam subramainiam as usual was very supportive. It is after eleven years I am accompaniying T.M. Krishna (I started my career with him in the year 1998) and it was a truly amazing experience. Surprisingly he remebered it when I told him.

“Please Don’t fail me!” – Decorator cries out to Template Method

This article is a result of serendipity that I experienced when implementing a small framework. As an ardent fan of design patterns I tend to use them where ever I could. I had a few classes in my framework in which I used the “Template Method” Design Pattern. When I wanted to extend my classes without modifying them, the first pattern that came to my mind was the Decorator Design Pattern. This article explains what problems I encountered during this implementation and how they were circumvented. Do these patterns gel well?

Follow the link Decorator Vs Template Method to find out the answer.

XML Configuration File Upgrade Technique

One of my colleagues asked me if there was a simple way to upgrade an xml configuration to one conforming to a new schema. Actually this is pretty easy and fun in .NET (if we use DataSets).
Here is an example

Old schema – OldEmployee.xsd

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" 

xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="EmployeeDetails">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" name="Employee">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="Name" type="xs:string" />
              <xs:element name="Designation" type="xs:string" />
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

New Schema – NewEmployee.xsd

<?xml version="1.0" encoding="utf-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" 

xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="EmployeeDetails">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" name="Employee">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="Name" type="xs:string" />
              <xs:element name="Designation" type="xs:string" />
              <xs:element name="Age" type="xs:positiveInteger" default="40"/>
              <xs:element name="Gender" type="xs:string" default="Male"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

The following code

• Reads the old schema into a data set
• Reads the old XML file (conforming to the old schema)
• Reads the new schema into a new data set
• Performs a merge on the new data set merging the old dataset
• Outputs the upgraded XML configuration file

using System.Data;

namespace ConfigFileUpgrade
{
   class Program
   {
      static void Main(string[] args)
      {
         DataSet dsOld = new DataSet();
         dsOld.ReadXmlSchema("OldEmployee.xsd");
         // Now lets try to read an XML conforming to this schema
         dsOld.ReadXml("OldEmployee.xml", XmlReadMode.Auto);

         // We create a new dataset and assign the new schema to it
         // This data set will not contain any data since we have read only the schema
         DataSet dsNew = new DataSet();
         dsNew.ReadXmlSchema("NewEmployee.xsd");

         // We merge the old data set with the new data
         // all the data in the old data set now gets merged to the new data set with
         // the new schema
         dsNew.Merge(dsOld, false, MissingSchemaAction.Add);

         // Upgrade is complete
         dsNew.WriteXml("NewEmployee.xml");
      }
   }
}

Increasing performance (.NET Regular Expressions)

I just discovered that the .NET Regex class offers a static method (CompileToAssembly) to compile a regular expression to an assembly for increased performance. Here is a sample code.

using System;
using System.Text.RegularExpressions;
using System.Reflection;

namespace CompiledRegEx
{
   class Program
   {
      static void Main(string[] args)
      {
         if ( args.Length < 5 )
         {
            Console.WriteLine("Error: Insufficient Parameters. \nUsage: rexc ");
            return;
         }

         string pattern = args[0];
         string options = args[1];
         string className = args[2];
         string namespaceName = args[3];
         string assemblyName = args[4];

         RegexCompilationInfo ri = new RegexCompilationInfo(pattern,
            (RegexOptions)Convert.ToInt32(options),
            className,
            namespaceName,
            true);

         Regex.CompileToAssembly(new RegexCompilationInfo[] { ri },
            new AssemblyName(assemblyName));

         Console.WriteLine("Regular Expression successfully compiled to an assembly");
      }
   }
}

You can now use the new type from the compiled assembly just as you would use any other type from an assembly. The Match method of the new RegEx type does not take the pattern as a parameter. If you use a lot of static regular expressions in your code, this can provide significant gain in performance.

Auto and Manual Reset Events Revisited

Just posted as article for Code Project on Auto and Manual Reset Events. I ended up writing this article after my bitter experience with analyzing some other group's log files and finding out the problem in their code was due to improper use of Manual Reset events.

Click HERE to read the article at CodeProject.

Type Safe Logging in C++

My Friend Vivek and I authored an article for Code Project. It is about Type Safe Logging in C++.

WPF data Binding using Custom Expressions

I was searching the web for some information about how to perform WPF data Binding using custom expressions. I came across an excellent article that explains this.

Here is the link: http://www.11011.net/wpf-binding-expressions