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MikeBevers.be

Putting it out there…

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Category: Software Development

Problem

If you don’t place a ‘not null’ condition before raising an event, you might get a NullReferenceException. That’s why we usually type something like:

event EventHandler MyEvent;

void RaiseMyEvent()
{
    if (MyEvent!= null) MyEvent(this, EventArgs.Empty);
}

Solution

Why not use the following pattern:

event EventHandler MyEvent = delegate { };

void RaiseMyEvent()
{
    MyEvent(this, EventArgs.Empty);
}

This way we can avoid the following:

Raising Events

Raising Events

Developing RegEx patterns

Recently I was creating some regular expressions. Because I’m not very experienced with RegEx, I was kind of “debugging” in my TDD approach. A colleague of mine recommended a website which helped a lot: http://www.gskinner.com/RegExr/.

It’s completely free and you can use it online!

Context

Before WCF, there was ASMX aka ASP.NET Web Services. Debugging ASMX or WCF are quite different. Let’s take a look how we can enable debugging in ASMX and WCF.

Basics of running a web application

When you hit the F5 button and your startup project is an ASP.NET, ASP.NET Web Services or WCF application, Visual Studio will start an ASP.NET Development Server. This is what we call Client-side hosting using Cassini. If want to know more check Dino Esposito’s article on MSDN. Wikipedia also has a description about UltiDev Cassini Web Server.

After Cassini is loaded, by default an Internet Explorer (IE) window will open and browse to the Cassini URL on your localhost.

Debugging ASMX

When you hit the F5 button, IE will open a webpage which looks like the image below:

Browse ASP.NET Web Service

Browse ASP.NET Web Service

You’ll notice that all Web Methods are listed as hyperlinks. So when I click “HelloWorld” in my example, it will browse forward:

Invoke ASP.NET Web Service

Invoke ASP.NET Web Service

Before we invoke the Web Method using IE, first we need to attach the Visual Studio instance with our sources to Cassini! In Visual Studio, navigate to “Debug” > “Attach to Process …”. In the list of Available Processes there should be a process called “WebDev.WebServer.exe” and the Title should be “ASP.NET Development Server – Port XXXX”. The Port XXXX is the port on which Cassini is active. Click the “Attach” button and you are ready to go!

Now, click the button “Invoke” in Internet Explorer and your Visual Studio will stop at the first breakpoint it encounters. When the method has returned its result, a new IE window will open and display the result as XML, like below:

ASP.NET Web Service Result

ASP.NET Web Service Result

 

Debugging WCF

Like ASMX, Visual Studio will open a browser by default:

Browse WCF Service

Browse WCF Service

At first it shows the directory listing. When you open your Service1.svc, you’ll notice that no hyperlinks or Invoke buttons are available on our Operation Contracts. To debug the WCF service, Microsoft provided a small tool in your Visual Studio installation directory, called “wcfTestClient.exe”. The tool is usually located in “C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\wcfTestClient.exe”. If not, you can download and install the Windows SDK from the Microsoft website.

In order to automatically start the “wcfTestClient.exe” and load our Services, we need to edit the WCF application project:

Start wcfTestClient.exe

Start wcfTestClient.exe

You can add multiple svc’s by leaving a space between the addresses.

When your WCF Service is loaded, you can double click an Operation Contract and invoke it. You don’t need to attach your Visual Studio to another process, it’s already attached for you.

wcfTestClient Method Invokation

wcfTestClient Method Invokation

Context

When you’re working with a UI or plain text data integration, conversions are often an issue. In this case I would like to talk about DateTime objects.

Recently, there was an issue in one of the other teams. They had a WinForms UI where they wanted to display a DateTime property in two different textboxes, one for the date and another for the time. They had their reasons for not using a DateTimePicker control or any other method. That wasn’t really the problem. One of the business users discovered an error when trying to save changes. The development team figured out what went wrong, apparently it was a “Culture” thing.

The business user’s computer was using Windows XP and its regional settings were set to English – United States. When the application tried to parse the textboxes and store the value back in the property, the month and day were swapped. In Europe we usually use “dd/MM/yyyy”, in the US they use “MM/dd/yyyy”.

Normally this should not pose a problem, the date was successfully loaded, so why wouldn’t it convert back as expected. Well, one of the main reasons is VB.NET. VB.NET has a feature called CDate, which can convert a string to a Date object. In C#, you only have a DateTime object. What happened? The CDate takes the regional settings and when you enter 16/10/2010, it will crash, because there is no 16th month.

Enter Mike

I overheard an intense discussion going on and decided to see if I could be of use. Call it interfering if you want; I see it as helping colleagues ;) . They explained the situation of the custom controls (the two textboxes) and the error. One of them was telling they needed to use DateTimePicker controls, another wanted to change regional settings in the database and application (I missed the point of that one), and so.

After a bit of evaluating, I noticed they were only complicating the solution/problem. I told them they only needed to parse the string into a DateTime object with specific format, and then assign the DateTime to the Date object. So instead of doing a lot of changes, add a single line of code…

I created a helper/utility class on the fly, so they could end their discussion and get back to work (and stop bothering the rest of us :) ).

DateTimeParser

using System;
using System.Globalization;

namespace MyNamespace
{
    public static class DateTimeParser
    {
        public static DateTime ParseDateTime(string value, string inputFormat)
        {
            return ParseDateTime(value, inputFormat, CultureInfo.InvariantCulture);
        }

        public static DateTime ParseDateTime(string value, string inputFormat, CultureInfo provider)
        {
            if (string.IsNullOrEmpty(value))
                throw new ArgumentNullException("value");

            try
            {
                return DateTime.ParseExact(value, inputFormat, provider);
            }
            catch (Exception ex)
            {
                throw new Exception("Could not parse date: " + value, ex);
            }
        }
    }

	public class DateTimeParserDemo
	{
		public DateTime Test()
		{
			string myDate = "31/12/2010 23:59:59";
			return DateTimeParser.ParseDateTime(myDate, "dd/MM/yyyy HH:mm:ss");
		}
	}
}

 

VB.NET code

If you prefer the code in VB.NET head to the website of DeveloperFusion.com, they have an excellent C# to VB.NET converter.

Context

Every developer knows that managing your app.config or web.config isn’t an enjoyable task. When you’re moving your application from one environment to another, you will need to change some variables. Maybe you’re working with automatic builds, and so on.

Since Visual Studio 2010 you have a new feature: “Config transformations”. Because I’m still working with Visual Studio 2008, I can’t use it. That’s why I wrote my own config transformer.

continue reading…

Context

I’m not a big fan of handling exceptions in stored procedures. It means that you have complicated queries, thus have some business logic in them. Although I like to keep my logic in code, sometimes it’s necessary to have some logic in your stored procedure.

Usually, I only use it to increase performance.

continue reading…

Context

What is a namespace? See Wikipedia.

For a company that builds its own software, namespaces are crucial to integrate applications. Maybe a stand-alone application that you’re building right now will one day be used as an external component. That’s why you need to use namespaces to identify your code.

continue reading…

Context

I was told that the internal IT development guidelines states that every project architecture must implement “Layering”, see Wikipedia. Three layers are required “DataLayer”, “BusinessLayer” and “UILayer”. Let’s go and take a look.

continue reading…

How they did what?

In this category I will discuss code that I run into: “How they did it”. Of course I will respond to it with: “How I do it”. To make things clear: I do/will not imply that my solution is the über-solution. I assume that my solution is better, why else would I make changes, but there always is a (small ;) )chance that I’m wrong.

I’d like to encourage every reader to share his view. Maybe, point out my mistakes or provide an even better solution. This is we all can learn the do’s and don’ts.

FYI: Every post in this category will begin with: “How they …”.

Background

Currently, I’m developing an application for a mobile device that runs on Windows XP Embedded. One of the requirements is that the application has to run in full screen mode. Also, a regular user should not be able to exit the application.

I was able to install the .NET 2.0 Framework on Windows XPe, so the front-end will be a WinForms 2.0 application.

continue reading…