C# Strings
C# Strings are used for storing text
The + operator can be used between strings to combine them. This is called concatenation.
string firstName = "Johan";
string lastName= “Vorster”;
Console.WriteLine(“Welcome ” + firstName + lastName);
You can also use the string.Concat() method to concatenate two strings:
string fullName = string.Concat(firstName, lastName);
Console.WriteLine(“Welcome ” + fullName);
// we could treat numbers as strings in some cases
string myX = “34”;
string myY = “45”;
Console.WriteLine(myX + myY); // the output will be 3445 – why?
Exercise: How could we change the code above so that a total value number is displayed?
- Option 1 hint – change the data types
- Option 2 hint – remember the lesson on type casting and conversion?
A string is an object
A string in C# is actually an object, which contain properties and methods that can perform certain
operations on strings. We will use only a few example methods today.
E.g. the length of a string can be found with the Length property:
string myTxt = "ABCDEFG";
Console.WriteLine("The length of the txt string is: " + myTxt.Length);
E.g. There are methods to convert the case of a string
string greet = "Hello World";
Console.WriteLine(greet.ToUpper()); // Outputs "HELLO WORLD"
Console.WriteLine(greet.ToLower()); // Outputs "hello world"
String Interpolation
NB. This is a newer feature introduced in Visual C# 6.0, so will not work in Visual Studio 2012, but
will work in later versions of Visual Studio
String interpolation allows programmers to substitutes values of variables into placeholders in a string.
Note that you do not have to worry about spaces, like with concatenation.
Also note that you have to use the dollar sign ($) when using the string interpolation method.
string firstName = "Johan";
string lastName = "Vorster";
string greeting = $"Welcome {firstName} {lastName}";
Console.WriteLine(greeting);
Access Characters Inside Strings
One way to think of a string is a sequence of individual characters. You can access the characters in a
string by referring to its index number inside square brackets [ ].
// To prints the first character from our existing string named greeting
Console.WriteLine(myString[0]); // Outputs "W"
NB: In C-type languages all indexes start with 0
- The first character in our example string is greeting[0]
- The second character is greeting[1]
- Etc
You can also find the index position of a specific character in a string, by using the IndexOf( ) method:
string myString = "Hello";
Console.WriteLine(myString.IndexOf("e")); // Outputs "1"
Another useful method is Substring(), which extracts the characters from a string, starting from the
specified character position/index, and returns a new string. This method is often used together with
IndexOf() to get the specific character position:
// Assume that a name contains a first name, space, followed by last name
// We want to find and print out the last name
Console.Write(“Please enter your first and last name: “);
string fullName = Console.ReadLine( );
// Find location of the space
int charPos = fullName.IndexOf(" ");
// Extract the last name
string lastName = fullName.Substring(charPos+1);
Console.WriteLine(“Your last name = ” + lastName);
Special Characters
Strings must be written within quotes, If you try to do the following, C# will misunderstand this string,
and generate an error. To solve problems like this we use special characters.
// this causes an error because of the quotes
string txt = "We are the so-called "Vikings" from the north.";
We can use the backslash escape character \ to turn special characters like quotes into normal string
characters.
Escape character Result
\' ‘ Single quote
\" “ Double quote
\\ \ Backslash
\n New Line
\t Tab
\b Backspace
// Examples with quotes
string txt1 = "We are called \"Vikings\". ";
Console.WriteLine(txt1);
// Example with single quote
string txt2 = "It\'s John\' apple!.";
Console.WriteLine(txt2);
// Example with backslash
string txt3 = "The character \\ is called backslash.";
Console.WriteLine(txt3);
Exercise: In a previous lesson we made use of the \n special character. Try using the other special
characters and see how it affects your output.
Adding Numbers and Strings
We’ve seen this in previous lessons and also today at the start of the lesson. REMEMBER that C# uses
the + operator for both addition and concatenation.
If the data used are numbers, they are added. Strings are concatenated.
// If you add two numbers, the result will be a number:
int x = 10;
int y = 20;
int z = x + y; // z will be 30 (an integer/number)
// If you add two strings, the result will be a string concatenation:
string x = "10";
string y = "20";
string z = x + y; // z will be 1020 (a string)
