LINQ Performance

http://msdn.microsoft.com/en-us/magazine/hh848257.aspx

(#elaborate)

Xsd2code

http://xsd2code.codeplex.com/

A tool which helps generate C# code from a XSD file. It can be very useful to generate classes which have a long list of properties - and you want to add WCF DataContract attributes, INotifyProperty code on these properties.

It also can be used when your application has lots of reference data. We can manually create XSD file with the reference data as enumeratio, then generate the class - and use this class in application. The class can be serialized and loaded back again if new items can be added by user.

There is also an option to auto-generate the classes if XSD file changes, I believe this requires installing a VS plug-in. The classes generated are partial classes, we can create another partial classes with same name if we want to add our own business rules.

#read: Code Generation in the .NET Framework Using XML Schema
http://msdn.microsoft.com/en-us/library/aa302301.aspx

Books (currently reading and to read)

Currently reading:

- Advanced MVVM

- LINQ in Action

- Pro LINQ

- WPF Unleashed

To read:

- Software Requirements:

http://shop.oreilly.com/product/9780735618794.do

- Pragmatic Programmer

http://www.amazon.com/Pragmatic-Programmer-Journeyman-Master/dp/020161622X

- The Passionate Programmer: Creating a Remarkable Career in Software Development (Pragmatic Life)
http://www.amazon.com/The-Passionate-Programmer-Remarkable-Development/dp/1934356344/ref=pd_sim_b_6

- Code generation in .NET

- Refactoring: Improving the Design of Existing Code

Regular Expression in LINQ

string[] companies = { "microsoft", "IBM", "oracle", "google", "apple", "facebook", "RIM" };
//wildcard search to "%o%o%"
Regex regex = new Regex("oo");
var oo = companies.Where(c => Regex.IsMatch(c, "o.*o")).Select(c => c);
var oo1 = from c in companies
		  where (Regex.IsMatch(c, "o.*o"))
		  select c;
oo1.Write();

Here we are searching for company names containing two “o”, need not be consecutive.

How to use LIKE, IN - in LINQ

How do we use LIKE (from SQL) in LINQ?

One option:
-> use string.Contains() method

string[] companies = { "microsoft", "IBM", "oracle", "google", "apple", "facebook" };
//get companies which have 'oo' in them
IEnumerable<string> companiesWithAnO = (from c in companies
                 where c.Contains("oo")
                 select c).ToArray();

Also we can use string.StartsWith() and EndsWith().

-> Second option: This is only if we are using LINQ To SQL.

string[] companies = { "microsoft", "IBM", "oracle", "google", "apple", "facebook" };
//get companies which have 'oo' in them
IEnumerable<string> companiesWithAnO = from c in companies
             where SqlMethods.Like(c,"%oo%")
             select c;

The IN operator is also quite easy.

string orangeFruit = "orange";
string[] fruitBasket = {"apple","orange","mango","leechy" };
//check orange is in the fruit basket
bool orangeFound = fruitBasket.Contains(orangeFruit);

“Contains” is the extension method in the IEnumerable<T> class.

LINQ: Differed Queries

LINQ queries, by default, are differed. It means that the original source collection is accessed only when the collection containing the LINQ output is enumerated. Let us see an example.

string[] companies = { "microsoft", "IBM", "oracle", "google", "apple", "facebook" };
//get companies which have 'oo' in them
IEnumerable<string> companiesWithAnO = from c in companies
           where c.Contains("oo")
           select c;
foreach (var item in companiesWithAnO)
{
 Console.WriteLine(item);
}

Output: google, facebook.

Let’s add a new line after the LINQ query.

try
{
 string[] companies = { "microsoft", "IBM", "oracle", "google", "apple", "facebook" };
 //get companies which have 'oo' in them
 IEnumerable<string> companiesWithAnO = from c in companies
       where c.Contains("oo")
       select c;
 //set IBM string to null
 companies[5] = null;
 foreach (var item in companiesWithAnO)
 {
  Console.WriteLine(item);
 }
}
catch (Exception ex)
{
 Console.WriteLine(ex.ToString());
}

O/P: Google, System.NullReferenceException…

So the first string “Google” is printed, but the next one gives error. Why? The reason is: when the LINQ query output variable – companiesWithAnO is enumerated, it accesses the original source collection – companies to get the results.

Let us check what the variable companiesWithAnO contains after the LINQ query but before the loop. Now we could check the companiesWithAnO.Count(), but this will give the output as 2, because running Count() will enumerate the collection – we need to prove that the collection companiesWithAnO hasn’t been enumerated and the original source not accessed yet.

We can try to have a look at the variable in debug mode, a breakpoint is set before the foreach loop.


The ‘Results View’ is not shown as it not yet enumerated. We change the query and add a ToArray().

IEnumerable<string> companiesWithAnO = (from c in companies
     where c.Contains("oo")
     select c).ToArray();

So the collection companiesWithAnO contains the values in this case.

Well we know now that LINQ queries are differed queries, except when we use ToArray() or ToList() or ToLookUp(). But why? We shall try that in next post.

LINQ: Extension Methods for Console apps

When designing Console apps for Windows, we usually write a lot of message to the console. It is a pain to write “Console.WriteLine(“xxxxxx”)” every time.

So let’s use extension methods to ease the pain.

Step 1> Create a Library project, add a class:

namespace LINQ.ExtensionMethods
{
    public static class MExtensions
    {
        public static void Write(this string s)
        {
            Console.WriteLine(s);
        }
    }
}

Step 2> Create a Console project, in the Main method:

        static void Main(string[] args)
        {
            "Welcome to Console project".Write();
        }

Let’s do this for a collection, no more writing loops or calling a method to iterate. Here we write an extension method for IEnumerable<T> in the class MExtensions above.

  public static void Write<T>(this IEnumerable<T> c)
        {
            Console.WriteLine();
            foreach (var item in c)
            {
                Console.WriteLine(item);
            }
        }

And to call:

    string[] games = { "Soccer", "Football", "Rugby" };
    var items = games.Select(p => new { p, p.Length });
    items.Write();

How to check when a machine was restarted?

Yesterday evening one of our test servers automatically rebooted. And today morning we found out that the last night’s test run was interrupted. Checking the logs and stuff, found out this was the case. So took on the task to find out what happened.

The best friend is Windows Event Logs – it is a reliable source to check computer’s history. (What happens in case of hibernate? #to-find)

Shutdown or reboot could happen because of various reasons and for each reason we could get a different Event ID. So we need is a quick way to find out the boot time . There are few events we can trust, the events logged by Event Logging service – that it is starting or shutting down. Very rarely would some one disable this service or start/stop it. The logs logged by Event Log Service are:

6005: logged at boot time, when the service starts
6006: at shutdown, that the service is stopping

The Date/Time of entries with these IDs can be taken as a rough idea when the computer stopped and booted.

In our case, we found that half an hour before a shutdown log – there was a log event (Event ID = 22, Category = Installation, Source = Windows Update Agent) logged by Windows Update – saying that the computer will be rebooted within 30 minutes.

More info: http://support.microsoft.com/kb/196452

Files to update in a patch

Think of references inside a as a way of selecting exactly what you want in your patch.

You have 2 options:

1: No with references inside them will result in all the differences between your target and upgrade being included.

2: Including with references inside them will result in only those things that are referenced being included in the patch.

Does that answer your question?

http://blogs.msdn.com/b/pmarcu/archive/2007/06/28/sample-patch.aspx

Wix: Set MSI filename based on version

A nice post on how to change the output MSI file name in Wix project based on the primary assembly’s version:

http://blog.tentaclesoftware.com/archive/2009/05/03/38.aspx

25 beautifully designed Windows apps

25 beautifully designed Windows apps:

http://windows.appstorm.net/roundups/25-beautifully-designed-windows-apps/