Strange behavior of FindElementsInHostCoordinates in WinRT



Silverlight features a splendid method: VisualTreeHelper.FindElementsInHostCoordinates. It allows the HitTest, i.e. makes it possible for a point or rectangle to search for all visual sub-tree objects that intersect this rectangle or point. Formally the same method VisualTreeHelper.FindElementsInHostCoordinates is available in WinRT. And it seems the method looks in the same way, but there is a little nuance. It works differently in different versions of the platform. So, let’s see what’s going on.


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About System.Drawing.Color and operator ==



Operator == that allows easy comparison of your objects is overridden for many standard structures in .NET. Unfortunately, not every developer really knows what is actually compared when working with this wonderful operator. This brief blog post will show the comparison logic based on a sample of System.Drawing.Color. What do you think the following code will get:

var redName = Color.Red;
var redArgb = Color.FromArgb(255, 255, 0, 0);
Console.WriteLine(redName == redArgb);

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Setting up build configuration in .NET



You get two default build configurations: Debug and Release, when creating a new project in Visual Studio. And it’s enough for most small projects. But there can appear a necessity to extend it with the additional configurations. It’s ok if you need to add just a couple of new settings, but what if there are tens of such settings? And what if your solution contains 20 projects that need setting up of these configurations? In this case it becomes quite difficult to manage and modify build parameters.

In this article, we will review a way to make this process simpler by reducing description of the build configurations.


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Jon Skeet's Quiz



Jon Skeet was once asked to give three questions to check how well you know C#. He asked the following questions:

  • Q1. What constructor call can you write such that this prints True (at least on the Microsoft .NET implementation)?
object x = new /* fill in code here */;
object y = new /* fill in code here */;
Console.WriteLine(x == y);

Note that it’s just a constructor call, and you can’t change the type of the variables.

  • Q2. How can you make this code compile such that it calls three different method overloads?
void Foo()
{
    EvilMethod<string>();
    EvilMethod<int>();
    EvilMethod<int?>();
}
  • Q3. With a local variable (so no changing the variable value cunningly), how can you make this code fail on the second line?
string text = x.ToString(); // No exception
Type type = x.GetType(); // Bang!

These questions seemed interesting to me, that is why I decided to discuss the solutions.


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Perfect code and real projects



I’ve got a problem. I am a perfectionist. I like perfect code. This is not only the correct way to develop applications but also the real proficiency. I enjoy reading a good listing not less than reading a good book. Developing architecture of a big project is no simpler than designing architecture of a big building. In case the work is good the result is no less beautiful. I am sometimes fascinated by how elegantly the patterns are entwined in the perfect software system. I am delighted by the attention to details when every method is so simple and understandable that can be a classic sample of the perfect code. But, unfortunately, this splendor is ruined by stern reality and real projects. If we talk about production project, users don’t care how beautiful your code is and how wonderful your architecture is, they care to have a properly working project. But I still think that in any case you need to strive for writing good code, but without getting stuck on this idea. After reading various holy-war discussions related to correct approaches to writing code I noticed a trend: everyone tries to apply the mentioned approaches not to programming in general, but to personal development experience, to their own projects. Many developers don’t understand that good practice is not an absolute rule that should be followed in 100% of scenarios. It’s just an advice on what to do in most cases. You can get a dozen of scenarios where the practice won’t work at all. But it doesn’t mean that the approach is not that good, it’s just used in the wrong environment. There is another problem: some developers are not that good as they think. I often see the following situation: such developer got some idea (without getting deep into details) in the big article about the perfect code and he started to use it everywhere and the developer’s code became even worse.
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To Add Comments or Not to Add?



A really good comment is the one you managed to avoid. (c) Uncle Bob

Lately, I’ve been feeling really tired of hot discussions on if it’s necessary to add comments in the code. As a rule, there are self-confident juniors with the indisputable statement as: “Why not to comment it, it will be unreadable without the comments!” on one side. And experienced seniors are on the other side. They understand that if it’s possible to go without the comments than “You better, damn it, do it in this way!” Probably, many developers got comment cravings since they’ve been students when professors made them comment every code line, “to make the student better understand it”. Real projects shouldn’t contain a lot of comments that only spoil the code. I don’t agitate for avoiding comments at all, but if you managed to write the code that doesn’t need comments, you can consider it your small victory. I would like to refer you to some good books that helped form my position. I like and respect these authors and completely share their opinion.


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Unexpected area to collect garbage in .NET



The .NET framework provides an intelligent garbage collector that saves us a trouble of manual memory management. And in 95% of cases you can forget about memory and related issues. But the remaining 5% have some specific aspects connected to unmanaged resources, too big objects, etc. And it’s better to know how the garbage is collected. Otherwise, you can get surprises.

Do you think GC is able to collect an object till its last method is complete? It appears it is. But it is necessary to run an application in release mode without debugging. In this case JIT compiler will perform optimizations that will make this situation possible. Of course, JIT compiler does it when the remaining method body doesn’t contain references to the object or its fields. It should seem a very harmless optimization. But it can lead to the problems if you work with the unmanaged resources: object compilation can be executed before the operation over the unmanaged resource is finished. And most likely it will result in the application crash.


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Unobviousness in use of C# closures



C# gives us an ability to use closures. This is a powerful tool that allows anonymous methods and lambda-functions to capture unbound variables in their lexical scope. And many programmers in .NET world like using closures very much, but only few of them understand how they really work. Let’s start with a simple sample:

public void Run()
{
  int e = 1;
  Foo(x => x + e);
}

Nothing complicated happens here: we just captured a local variable e in its lambda that is passed to some Foo method. Let’s see how the compiler will expand such construction.*

public void Run()
{
  DisplayClass c = new DisplayClass();
  c.e = 1;  
  Foo(c.Action);
}
private sealed class DisplayClass
{
  public int e;
  public int Action(int x)
  {
    return x + e;
  }
}

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Wrapping C# class for use in COM



Let us have a C# class that makes something useful, for example:

public class Calculator
{
    public int Sum(int a, int b)
    {
        return a + b;
    }
}

Let’s create a COM interface for this class to make it possible to use its functionality in other areas. At the end we will see how this class is used in Delphi environment.


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About



Andrey Akinshin is a software developer, a frequent conference speaker, an author of blog posts and papers. He is the project lead of BenchmarkDotNet (the most popular .NET library for benchmarking) and perfolizer (performance analysis toolkit); the author of Pro .NET Benchmarking (a book about good practices of performance measurements). Currently, Andrey is a software developer at JetBrains, where he works on Rider (a cross-platform .NET IDE based on the IntelliJ platform and ReSharper). He is also the program director of the DotNext conference, an ex Microsoft .NET MVP, a silver medalist of ACM ICPC. Andrey is a PhD in computer science. He is involved in a research project at the Sobolev Institute of Mathematics SB RAS related to the mathematical biology and bifurcation theory. Previously, he worked as a postdoctoral research fellow at the Weizmann Institute of Science.
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