Strings are one of the most important data types in any modern language including C#. In this article, you will learn how to work with strings in C#. The article discusses the String class, its methods and properties and how to use them.
The System.String data type represents a string in .NET. A string class in C# is an object of type System.String. The String class in C# represents a string.
The following code creates three strings with a name, number, and double values.
// String of characters System.String authorName = "Susheel Kumar"; // String made of an Integer System.String age = "33"; // String made of a double System.String numberString = "33.23";
Here is the complete example that shows how to use stings in C# and .NET.
using System; namespace CSharpStrings { class Program { static void Main(string[] args) { // Define .NET Strings // String of characters System.String authorName = "Susheel Kumar"; // String made of an Integer System.String age = "33"; // String made of a double System.String numberString = "33.23"; // Write to Console. Console.WriteLine("Name: {0}", authorName); Console.WriteLine("Age: {0}", age); Console.WriteLine("Number: {0}", numberString); Console.ReadKey(); } } }
Create a string
There are several ways to construct strings in C# and .NET. Create a string using a constructorCreate a string from a literalCreate a string using concatenationCreate a string using a property or a methodCreate a string using formatting Create a string using its constructor
The String class has several overloaded constructors that take an array of characters or bytes. The following code snippet creates a string from an array of characters.
char[] chars = { 'S', 'u', 's', 'h', 'e', 'e' , 'l'}; string name = new string(chars); Console.WriteLine(name);
Create a string from a literal
This is the most common ways to instantiate a string.
You simply define a string type variable and assign a text value to the variable by placing the text value without double quotes. You can put almost any type of characters within double quotes accept some special character limitations.
The following code snippet defines a string variable named firstName and then assigns text value Susheel to it.
string firstName; firstName = "Susheel";
Alternatively, we can assign the text value directly to the variable.
string firstName = "Susheel";
Here is a complete sample example of how to create strings using literals.
using System; namespace CSharpStrings { class Program { static void Main(string[] args) { string firstName = "Susheel"; string lastName = "Kumar"; string age = "26"; string numberString = "33.23"; Console.WriteLine("First Name: {0}", firstName); Console.WriteLine("Last Name: {0}", lastName); Console.WriteLine("Age: {0}", age); Console.WriteLine("Number: {0}", numberString); Console.ReadKey(); } } }
Create a string using concatenation
Sting concatenation operator (+) can be used to combine more than one string to create a single string. The following code snippet creates two strings. The first string adds a text Date and current date value from the DateTime object. The second string adds three strings and some hard coded text to create a larger string.
string nowDateTime = "Date: " + DateTime.Now.ToString("D"); string firstName = "Susheel"; string lastName = "Kumar"; string age = "26"; string authorDetails = firstName + " " + lastName + " is " + age + " years o ld."; Console.WriteLine(nowDateTime); Console.WriteLine(authorDetails);
Create a string using a property or a method
Some properties and methods of the String class returns a string object such as SubString method. The following code snippet takes one sentence string and finds the age within that string. The code returns 26.
string authorInfo = "Susheel Kumar is 26 years old."; int startPosition = sentence.IndexOf("is ") + 1; string age = authorInfo.Substring(startPosition +2, 2 ); Console.WriteLine("Age: " + age);
Create a string with Format
The String.Format method returns a string. The following code snippet creates a new string using the Format method.
string name = "Susheel Kumar"; int age = 26; string authorInfo = string.Format({0} is {1} years old.", name, age.ToString()); Console.WriteLine(authorInfo);
Create a string using ToString Method
The ToString method returns a string. We can apply ToString on pretty much any data type that can be converted to a string. The following code snippet converts an int data type to a string.
string name = "Susheel Kumar"; int age = 26; string authorInfo = string.Format({0} is {1} years old.", name, age.ToString()); Console.WriteLine(authorInfo);
Get all characters of a string using C#
A string is a collection of characters.
The following code snippet reads all characters of a string and displays on the console.
string nameString = "Susheel Kumar"; for (int counter = 0; counter <= nameString.Length - 1; counter++) Console.WriteLine(nameString[counter]);
Size of string
The Length property of the string class returns the number of characters in a string including white spaces.
The following code snippet returns the size of a string and displays on the console.
string nameString = "Susheel Kumar"; Console.WriteLine(nameString); Console.WriteLine("Size of string {0}", nameString.Length);
Number of characters in a string
We can use the string.Length property to get the number of characters of a string but it will also count an empty character. So, to find out the exact number of characters in a string, we need to remove the empty character occurrences from a string.
The following code snippet uses the Replace method to remove empty characters and then displays the non-empty characters of a string.
string name = "Susheel Kumar"; string name = "Susheel Kumar"; // Get size of string Console.WriteLine("Size of string: {0}", name.Length ); // Remove all empty characters string nameWithoutEmptyChar = name.Replace(" ", ""); // Size after empty characters are removed Console.WriteLine("Size of non empty char string: {0}", nameWithoutEmptyChar.Length); // Read and print all characters for (int counter = 0; counter <= nameWithoutEmptyChar.Length - 1; counter++) Console.WriteLine(nameWithoutEmptyChar[counter]);
Convert String to Char Array
ToCharArray method converts a string to an array of Unicode characters. The following code snippet converts a string to char array and displays them.
string sentence = "Susheel Kumar is an author and developer in CoderArts"; char[] charArr = sentence.ToCharArray(); foreach (char ch in charArr) { Console.WriteLine(ch); }
Empty String
An empty string is a valid instance of a System.String object that contains zero characters. There are two ways to create an empty string. We can either use the string.Empty property or we can simply assign a text value with no text in it.
The following code snippet creates two empty strings.
string empStr = string.Empty; string empStr2 = "";
Both of the statements above generates the same output.
An empty string is sometimes used to compare the value of other strings. The following code snippet uses an empty string to compare with the name string.
string name = "Susheel Kumar"; if (name != empStr) { Console.WriteLine(name); }
In real-world coding, we will probably never create an empty string unless you plan to use it somewhere else as a non-empty string. We can simply use the string.Empty direct to compare a string with an empty string.
if (name != string.Empty) { Console.WriteLine(name); }
Here is a complete example of using an empty string.
string empStr = string.Empty; string empStr2 = ""; string name = "Susheel Kumar"; if (name != empStr) { Console.WriteLine(name); } if (name != string.Empty) { Console.WriteLine(name); }
Null String
A null string is a string variable that has not been initialized yet and has a null value. If you try to call any methods or properties of a null string, you will get an exception. A null string valuable is exactly the same as any other variable defined in your code.
A null string is typically used in string concatenation and comparison operations with other strings.
The following code example shows how to use a null string.
string nullStr = null; string empStr = string.Empty; string name = "Susheel Kumar"; if ((name != nullStr) || (name != empStr)) { Console.WriteLine(name + " is neither null nor empty"); }