In response to a web-forum question, I found myself writing a little C# to convert from a string (containing a binary number) into the integer representation of the same. It’s the kind of trivial coding problem that first year programmers would come up against… Of course, we could make it harder by stipulating that we cannot use System.Convert.

I’m sure that there are much better ways of doing this, and I’d be glad to see some of them appear in the comments for this post. There, a kind of challenge…If the quality of the comments is good enough, I might be able to offer a small prize if you are a UK resident. No promises though!

[code lang=”C#”]
public int BinToInt(string binaryNumber)
{
int multiplier = 1;
int converted = 0;

for (int i = binaryNumber.Length – 1; i >= 0; i–)
{
int t = System.Convert.ToInt16(binaryNumber[i].ToString());
converted = converted + (t * multiplier);
multiplier = multiplier * 2;
}
return converted;
}
[/code]

In use:

[code lang=”C#”]
// remember SEFTU, sixteen, eight, four, two, one
listBox1.Items.Add(BinToInt(“00001”).ToString()); // 1
listBox1.Items.Add(BinToInt(“00010”).ToString()); // 2
listBox1.Items.Add(BinToInt(“00011”).ToString()); // 3
listBox1.Items.Add(BinToInt(“00100”).ToString()); // 4
listBox1.Items.Add(BinToInt(“00101”).ToString()); // 5
listBox1.Items.Add(BinToInt(“00111”).ToString()); // 7
listBox1.Items.Add(BinToInt(“01000”).ToString()); // 8
listBox1.Items.Add(BinToInt(“10000”).ToString()); // 16[/code]

It might be of use to somebody…somewhere…

It is a fairly common programming scenario to find ourselves with a list of identical objects. In the past, without adequate support from programming languages, we found ourselves writing a lot of searching and sorting code, and that may have put you off using lists in favour of arrays. All that has changed with C# (particularly 2.0) – its implementation of a list makes handling such lists remarkably easy.

For example, given the following class Person:

[code lang=”C#”]
public class Person
{
public int age;
public string name;

public Person(int age, string name)
{
this.age = age;
this.name = name;
}
}
[/code]

We can create a list of Person objects and add six people like so:

[code lang=”C#”]
Listpeople = new List();

people.Add(new Person(50, “Fred”));
people.Add(new Person(30, “John”));
people.Add(new Person(26, “Andrew”));
people.Add(new Person(24, “Xavier”));
people.Add(new Person(5, “Mark”));
people.Add(new Person(6, “Cameron”));
[/code]

C#’s list mechanism provides us with a number of useful methods. Personally, I find ForEach, FindAll and Sort to be very useful. ForEach allows us access to each item in the list. FindAll allows us to search for objects in the list that match a specific condition. Sort allows us to sort the objects in the list. The following code demonstrates how we might use each of these methods:

[code lang=”C#”]

Console.WriteLine(“Unsorted list”);

people.ForEach(delegate(Person p)
{ Console.WriteLine(String.Format(“{0} {1}”, p.age, p.name)); });

// Find the young
List young = people.FindAll(delegate(Person p) { return p.age < 25; }); Console.WriteLine("Age is less than 25"); young.ForEach(delegate(Person p) { Console.WriteLine(String.Format("{0} {1}", p.age, p.name)); }); // Sort by name Console.WriteLine("Sorted list, by name"); people.Sort(delegate(Person p1, Person p2) { return p1.name.CompareTo(p2.name); }); people.ForEach(delegate(Person p) { Console.WriteLine(String.Format("{0} {1}", p.age, p.name)); }); // Sort by age Console.WriteLine("Sorted list, by age"); people.Sort(delegate(Person p1, Person p2) { return p1.age.CompareTo(p2.age); }); people.ForEach(delegate(Person p) { Console.WriteLine(String.Format("{0} {1}", p.age, p.name)); }); [/code] And here is the output that we should expect: Unsorted list
50 Fred
30 John
26 Andrew
24 Xavier
5 Mark
6 Cameron

Age is less than 25
24 Xavier
5 Mark
6 Cameron

Sorted list, by name
26 Andrew
6 Cameron
50 Fred
30 John
5 Mark
24 Xavier

Sorted list, by age
5 Mark
6 Cameron
24 Xavier
26 Andrew
30 John
50 Fred

Lists are powerful and result in fewer, and more elegant, lines of code. Hopefully this short example has demonstrated their ease and you will find yourself using them in your day-to-day development activities.