Using an integer to store multiple values in C#

Suppose that you are creating a game in which your character obtains some awards out of some predefined one, as the game goes by. Or, you’re creating software in which you want your user to select some entries/items (imagine something like a checked list box). In both cases, you could try and use these two approaches

  1. Create or use a data structure (e.g. Dictionary<K,V>) in which you store a reference to all possible items along with the relevant Boolean value. Easy right? In order to answer the question if user has obtained item X, you just check the value of the relevant key in the dictionary.
  2. Create or use a data structure (e.g. List<T>) in which you store references to the items the user has obtained/picked. So, you can use the List.Contains method to check for an item’s existence.

Both described methods are efficient, easy to grasp and use. However, there is another method in which you do not need to use nothing more advanced than a simple integer. We’ll be using binary system arithmetic and logic to accomplish this purpose.

Each number can be written in binary format in a sequence of 1s and 0s. For instance, 15 is binary 1111 and 2 is binary 0010. Most importantly, all numbers that are a power of two start with 1 and finish with some 0s. Check the below list

Binary – Base 10

So, if you assign e.g. “valueA”to 1, “valueB” to 2, “valueC” to 4 etc., you can easily assign multiple values into an integer. How? You just add the relevant base 10 value to this integer, let’s call it storage. For instance, the integer 13 contains 3 values: a)1, b)4, c)8. In binary form, it is written as 1101. The way to check for a value’s existence is a logical bitwise AND between the storage and the respective value. In C#, we use the & for this purpose. If the result of the operation is equal to the value, then storage contains this value. Simple, right? Check the below C# code for the value 19.

int storage = 19; //10011
int a = 1; //1
int b = 2; //10
int c = 4; //100
int d = 8;//1000
int e = 16;//10000
Console.WriteLine("Check for the value 19 - 10011");
Console.WriteLine($"Does {storage} contain \"a\" with the value of 1? " + ((storage & a) == a)); //true
Console.WriteLine($"Does {storage} contain \"b\" with the value of 2? " + ((storage & b) == b)); //true
Console.WriteLine($"Does {storage} contain \"c\" with the value of 4? " + ((storage & c) == c)); //false
Console.WriteLine($"Does {storage} contain \"d\" with the value of 6? " + ((storage & d) == d)); //false
Console.WriteLine($"Does {storage} contain \"e\" with the value of 8? " + ((storage & e) == e)); //true

Read More »

My .NET and C# samples

Recently, I uploaded on GitHub a lot of .NET and C# samples I have created over the years, as part of my presentations and trainings. You can find them here and download them. All the samples are comprised of  few lines of code that do a specific thing, relevant to the sample’s name. Some of the samples are pretty old and have been superceded by new language/framework advancements (e.g. Linq To XML vs XmlReader) but I’ve decided to keep them in case they prove useful to someone. Small description follows for each sample below:

  • C# Arguments – demonstrates usage of arguments in C# methods
  • Chat with TCP – a chat server and client using the TCP protocol
  • Collections – usage of .NET collections
  • Complex – usage of operator overloading
  • Default Arguments – demo of Parallel.ForEach
  • Delegates – usage of delegates in C#
  • DirectorySearcher – search directories using the DirectoryInfo class
  • DownloadString – WebClient demo
  • Events – simple Button.Click event handling
  • Exceptions – demo of Thread.Abort
  • Extension Methods – C# extension methods
  • Fibonacci – recursively calculating the Fibonacci sequence in C# using Func delegate
  • FileReaderWriter  – FileStream, StreamReader and StreamWriter demo on how to read and write to a file using C#
  • FileSystemWatcher – get notified of file system events (file created, deleted etc.)
  • Generics and IO – demo of a generic Dictionary being written and read from a file
  • Globalization – using globalization classes to display currencies and date/time information in a variety of countries
  • HttpWebRequest – HttpWebRequest demo to connect to an HTTP server
  • MD5 Hashing  – MD5 hashing using C#
  • MultiplyMatrices – multiply two matrices
  • Object Serialization – serialize an object using XmlSerializer class
  • Processes enumeration – get processes that are currently running on your machine
  • Reflection – use reflection in C# to discover information about unknown types and classes
  • Regex and pattern matching – use of regular expressions in C#
  • SendMail – how to send e-mail using C#
  • StopWatch – using a stopwatch in C# to count passing time
  • StringBuilder – an efficient class for heavy string manipulation
  • Threading – how to use threads in C# using classes in the System.Threading namespace
  • Timers – how to use timers in C#
  • XML DOM – read XML via XmlTextReader class

Read More »

Comparison σε List

Στο παρακάτω link έχω ανεβάσει ένα solution με μια console C# 3.0 εφαρμογή, στην οποία μπορείτε να δείτε 3 τρόπους για να κάνουμε comparison με χρήση της μεθόδου List<T>.Sort(); με χρήση

  • delegate / lambda τύπου Comparison<T>
  • IComparer<T>
  • IComparable<T>

Τo link είναι

Μπορείτε να ποστάρετε comment για οποιαδήποτε απορία έχετε!!