Skip to main content

C# Brainteasers

Here's some code using the anonymous method feature of C# 2. What does it do?

using System;
using System.Collections.Generic;

class Test
{
    delegate void Printer();
   
    static void Main()
    {
        List<Printer> printers = new List<Printer>();
        for (int i=0; i < 10; i++)
        {
            printers.Add(delegate { Console.WriteLine(i); });
        }
       
        foreach (Printer printer in printers)
        {
            printer();
        }
    }
}

Answer: Ah, the joys of captured variables. There's only one i variable here, and its value changes on each iteration of the loop. The anonymous methods capture the variable itself rather than its value at the point of creation - so the result is 10 printed ten times!
Labels:

Comments

Post a Comment

Popular posts from this blog

gcAllowVeryLargeObjects Element

There are numerous new features coming with .NET 4.5 and here, on this blog, you can find several posts about it. But the feature we are goint to talk about today is very exciting, because we were waiting for it more than 10 years. Since .NET 1.0 the memory limit of .NET object is 2GB. This means you cannot for example create array which contains elements with more than 2GB in total. If try to create such array, you will get the OutOfMemoryException. Let’s see an example how to produce OutOfMemoryException. Before that Open Visual Studio 2012, and create C# Console Application, like picture below. First lets create simple struct with two double members like example below: 1 2 3 4 5 6 7 8 9 10 11 12 public struct ComplexNumber {      public double Re;      public double Im;      public ComplexNumber( double re, double im)      {          Re=re;          Im=im;      } } As we know this structure consumes about 16
Post a Comment
Read more

Support for debugging lambda expressions with Visual Studio 2015

Anyone who uses LINQ (or lambdas in general) and the debugger will quickly discover the dreaded message “Expression cannot contain lambda expressions”. Lack of lambda support has been a limitation of the Visual Studio Debugger ever since Lambdas were added to C# and Visual Basic.  With visual studio 2015 Microsoft has added support for debugging lambda expressions. Let’s first look at an example, and then I’ll walk you through current limitations. Example To try this yourself, create a new C# Console app with this code: using System.Diagnostics; using System.Linq; class Program { static void Main() { float[] values = Enumerable.Range(0, 100).Select(i => (float)i / 10).ToArray(); Debugger.Break(); } } Then compile, start debugging, and add “values.Where(v => (int)v == 3).ToArray()” in the Watch window. You’ll be happy to see the same as what the screenshot above shows you. I am using Visual Studio 2015 Preview and it has some limitations.
1 comment
Read more

How to allow a very large object in .net application?

Since .NET 1.0 the memory limit of .NET object is 2GB. This means you cannot for example create array which contains elements with more than 2GB in total. If try to create such array, you will get the OutOfMemoryException. Let’s see an example how to produce OutOfMemoryException. Before that Open Visual Studio, and create C# Console Application. Lets create simple struct with two double members like example below: public struct ComplexNumber { public double Re; public double Im; public ComplexNumber(double re, double im) { Re = re; Im = im; } } As we know this structure consumes about 16 bytes of memory. So if we want to create array of this type which consume more than 2GB we need to create array at least with 134217728 instances. So this sample program below creates 130000000 (about 1,97 GB) of array. int maxCount = 130000000; ComplexNumber[] arr = null; try { arr = new ComplexNumber[maxCount]; } catch (Exception ex) { Console.WriteLine(ex.Message); } So if we run t
Post a Comment
Read more