C# Strings Tutorial

What is a string

In C# we have the benefit of the keyword string to combine single characters into words and sentences.

In fact, a string is actually an array of characters. In languages such as C, we can’t use a string. We have to explicitly define arrays of characters.

#include <stdio.h>
int main()
{
    char message[] = "Hello World";

    printf(message);

    return 0;
}

Even though the example above is a different language, we can see that the string Hello World has to be defined as an array of chars.

How to create a string object

In C# we have multiple ways to create a string object:

• Assign a string literal to a String variable
• Use a String class constructor
• Use the string concatenation operator (+)
• Use the string concatenation function
• Retrieve a property or calling a method that returns a string
• Call a formatting method to convert a value or an object to its string representation

Each of these will apply to the specific situation we need them in.

String literal

The most common method to create a string is to create a string literal. We do this by assigning a string value to a string variable.

string identifier = "value";

using System;

namespace Strings
{
    class Program
    {
        static void Main(string[] args)
        {
            string message = "Hello World";

            Console.WriteLine(message);
            Console.ReadLine();
        }
    }
}

In the example above, we store our string in a variable.

String constructor

We can create a new string object with the string class constructor.

using System;

namespace Strings
{
    class Program
    {
        static void Main(string[] args)
        {
            // char array
            char[] letters = { 'H', 'e', 'l', 'l', 'o' };

            // string of char array
            string greeting = new string(letters);

            Console.WriteLine(greeting);
            Console.ReadLine();
        }
    }
}

String concatenation

When multiple strings are combined (concatenated) it creates a new string. A string is concatenated with the + operator.

The compiler will concatenate a string when the + operator is used on strings, but will perform mathematical operations on numbers.

using System;

namespace Strings
{
    class Program
    {
        static void Main(string[] args)
        {
            string firstName = "Peter";
            string lastName = "Parker";

            Console.WriteLine(firstName + " " + lastName);
            Console.ReadLine();
        }
    }
}

Function that returns a string

A new string is created when we return a string from a function. The new string can be stored in a variable or used directly.

using System;

namespace Strings
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Message());
            Console.ReadLine();
        }

        static string Message()
        {
            return "Hello World";
        }
    }
}

In the example above, we use the newly created string directly in the WriteLine() function.

String formatting function

We can use any string formatting function, like the WriteLine() or Format() function, to create a string.

using System;

namespace Strings
{
    class Program
    {
        static void Main(string[] args)
        {
            string firstName = "Bruce";
            string lastName = "Wayne";

            Console.WriteLine("Name: {0} {1}", firstName, lastName);
            Console.ReadLine();
        }
    }
}

using System;

namespace Strings
{
    class Program
    {
        static void Main(string[] args)
        {
            DateTime dob = new DateTime(1986, 08, 07);
            string formattedDob = String.Format("Date of Birth: {0:D}", dob);

            Console.WriteLine(formattedDob);
            Console.ReadLine();
        }
    }
}

A list of common properties of the String class

The following table shows some of the most commonly used properties of the String class.

A list of common methods of the String class

The following table shows some of the most commonly used functions of the String class.

Summary: Points to remember

• A string is a collection of ASCII characters that forms words and sentences.
• In C#, we have several options to create a string.
  • The most common option is to initialize a string literal.
  • We can also create a string object with its class constructor.
  • Any time we combine more than one string, a new string is created.
  • Any function that returns a string will create a new string.
  • Any function that formats a string, like WriteLine() or Format() will create a new string from their inputs.