title: “Exploring Built-In Functions” —

Exploring Built-In Functions

The C# language actually has a lot of built-in functionality in the form of classes and functions. We’ll talk more about Classes in the next lesson.

But let’s explore some of the built-in functions that are available to us!

Working with strings

There are lots of interesting things you can do with strings, such as analyzing user input text.

Go find the C# documenation for strings, and learn about the following string functions:

Replace
Contains

For instance, you could write a program that tells you whether an input string contains the word “banana”;

string userInput = Console.ReadLine();
bool containsYes = userInput.Contains("banana");
Console.WriteLine(" Contains the word 'banana': " + containsYes);

Open a webpage:

Here’s a bit of code that will open a browser window to a webpage the user specifies:

Console.WriteLine("What webpage would you like to visit? Be sure to put http:// at the beginning!");
string webPage = Console.ReadLine();
System.Diagnostics.Process.Start("explorer", webPage);

Open file contents:

Here’s a bit of code that will load the contents of a text file from a particular location on the hard drive, and print the contents to the console:

	//read all the contents of a file 
	//NOTE: (You need to go to the c:\Users\Public\ folder in Windows Explorder, make a new folder called "Test", and then make a new text file there called test.txt)
	//alternatively, you could make this program ask the user for a path
	string contents = System.IO.File.ReadAllText("C:\\Users\\Public\\Test\\text.txt");
	Console.WriteLine("File contents: " + contents);

You can use File.ReadAllLines to read all of the text out of a file.

Math

C# comes with a whole library of math functions called MathF. For instance, here’s a function to compute the area of a circle given its radius, using the MathF.PI variable:

float ComputeCircleArea(float radius)
{
	return MathF.PI * (radius * radius);
}

What do you want to do with your code?

Not sure how to do a particular thing in code? Chances are, there are samples out on the internet! One of the most important skills you’ll develop as a programmer is figuring out how to find existing solutions for problems.
Google is your friend!