I had read about Code Contracts long time ago, but I didn’t see a reason to use contract instead of simple tests and argument's check with Exception's throws. Only now I’m trying to use them at real project. I didn’t see why I need to write:

Contract.Requires<ArgumentNullException>(argument == null); 

Instead of like I did it before:

if (argument == null) 

    throw new ArgumentNullException(“argument”)

Couple of weeks ago I had reinstall my Windows 7 on my laptop (I bought SSD for my laptop). After I install ReSharper with Visual Studio 2010 after run I accidental choosed “Go to the metadata” instead of like usual “Go to Object Explorer” by Ctrl and Mouse Click. So when I clicked on some class of System.xxx (basic classes of .NET) I looked at source code of these classes and found that they are using Code Contracts. I thought this is why I need to understand why I need to use contracts in my code, so I started to use them in some small applications and tried to find some interesting case.

Couple days ago I got a question about how to register hotkey in Windows for WPF application. I remembered that one year ago I was solving the same problem in WinForms application, I was registering hot keys for my application, it was Vista Keys Extender project. I knew that my project worked, so I suggested author of question to use code of my project to solve his problem. But as we learned later in WPF message handle mechanism different from WinForms. So I started to find solution for WPF application. I copied my old code from my old project and started to rewrite it step-by-step.

Couple of weeks ago I wrote about my small utility Config Transformation Tool, which I wrote with base of web.config transformation task. In those moments I was thinking about opportunity to pass parameters to transform file, to tool can replaces parameters in transformation file with special values. Yesterday I resolved this issue. From now I use class Microsoft.Web.Publishing.Tasks.XmlTransformation which works with strings and XmlDocuments instead of files. I had two tasks: (a) I need method which will replace parameters on values, (b) I need method which will be parse command line and create dictionary of parameters.

Couple of weeks ago I got a paper copy of book Pablo Cibraro, Kurt Claeys, Fabio Cozzolino, Johann Grabner - Professional WCF 4: Windows Communication Foundation with .NET 4. This book has not a lot of pages, just about 400. Really, I don’t remember when I saw so thin book about some technology. But maybe this book has not a lot pages, but a lot of interesting themes.

First chapter is patterns and principles of SOA applications. This is the best chapter in this book. When I was reading this chapter I saw that authors have a lot experience of creating applications with Service-oriented architecture. Authors described all possible architecture principles, with which you can create SOA applications. And they did not limit themselves to the principles that are possible with WCF. I think that this chapter is “must read” for all developers, it is doesn’t matter what technologies you are using: php, java or .net. And this is good luck that Wrox published this chapter online: Design Principles and Patterns. It is about 30 pages, so read it right now.

At our product we have a client Silverlight part and server-code part, which contains a lot of WCF methods. We don’t use ASP.NET Compatible mode, because we want to leave an opportunity to deploy server part to server without web-server role (without IIS). Really, I don’t know why we chose this way, because all of our installations at current moment are on IIS. But we have what we have, so we haven’t ASP.NET Compatible mode, and as an expected result we can’t get HttpContext.Current instance at server WCF methods. One of WCF Service is a RESTful service, which at his methods returns report files, so it can handle GET-queries from browsers.

Just became a lucky owner of this book C# IN A NUTSHELL 4th edition. This is a fourth edition of this book’s series. I saw previous third edition of this book, we presented it on one of our events at Yaroslavl State University, but that book was a Russian translated version and published in Russia, this is was bad side of that book – all books at Russia printed on really bad paper. I should say that I didn’t read this book by end, but already I was surprised. Why? Why I heard a lot about Richter CLR via C# (English version of 3rd edition of this book I already have, and this book are waiting my attention), and just a few words about C# IN A NUTSHELL, at least in my sphere. I just listen once about this book at one of the podcast of Alt.Net group, and this words was Richter it is really good book, and C# IN A NUTSHELL it is a good handbook. My opinion is - you should read Richter if you want to develop with .NET. But if you want to develop on .NET with C# you should read C# IN A NUTSHELL too.

Data export from DataGrid to Excel is very common task, and it can be solved with different ways, and chosen way depend on kind of app which you are design. If you are developing app for enterprise, and it will be installed on several computes, then you can to advance a claim (system requirements) with which your app will be work for client. Or customer will advance system requirements on which your app should work. In this case you can use COM for export (use infrastructure of Excel or OpenOffice). This approach will give you much more flexibility and give you possibility to use all features of Excel app. About this approach I’ll speak below. Other way – your app is for personal use, it can be installed on any home computer, in this case it is not good to ask user to install MS Office or OpenOffice just for using your app. In this way you can use foreign tools for export, or export to xml/html format which MS Office can read (this approach used by JIRA). But in this case will be more difficult to satisfy user tasks, like create document with landscape rotation and with defined fields for printing.

At this article I'll show you how to work with Excel object from .NET 4 and Silverlight 4 with dynamic objects and give you an approach which allow you to export data from DataGrid Silverlight and WPF controls.

In Windows 7, I really liked an opportunity to change the position of the windows by pressing hotkeys Win + (Left | Right | Up | Bottom):

• Win + Left - window attached to the left side
• Win + Right - window attached to the right side
• Win + Up - window is maximized
• Win + Bottom - window in the normal state

So I spent my time and wrote this tool for Vista/XP users.

Recently I read good Russian post with many interesting extensions methods after then I remembered that I too have one good extension method “Safely type convert”. Idea of this method I got at last job.

We often write code like this:

int intValue;

if (obj == null || !int.TryParse(obj.ToString(), out intValue))

    intValue = 0;

This is method how to safely parse object to int. Of course will be good if we will create some unify method for safely casting.

I found that better way is to create extension methods and use them then follows:

int i;

i = "1".To<int>();

// i == 1

i = "1a".To<int>();

// i == 0 (default value of int)

i = "1a".To(10);

// i == 10 (set as default value 10)

i = "1".To(10);

// i == 1

// ********** Nullable sample **************

int? j;

j = "1".To<int?>();

// j == 1

j = "1a".To<int?>();

// j == null

j = "1a".To<int?>(10);

// j == 10

j = "1".To<int?>(10);

// j == 1

I should say that I’m fan of regular expressions. Whenever I see the problem, which I can solve with Regex, I felt a burning desire to do it and going to write new test for new regex. Previously I had installed SharpDevelop Studio just for good regular expression tool in it (Why VS doesn’t have one?). But now I’m a little wiser, and for each Regex I write a separate test.

I find it difficult to remember the syntax of regular expressions (I don’t write them very often); I always forget which character is responsible for the beginning of the line, etc. So I use external small and easy articles like this “Regular expressions - An introduction”.

Now I want to show you little samples of regular expressions and want to show you how to test these samples.