String manipulations

In C#, a string is reference type data type that is used to represent a sequence of characters. It is declared with "string" keyword which is a wrapper around System.String class. We can also say that string is an array of characters represented in a concise way. String manipulation is a very important feature in any programming language because it is used to operate on textual data. In general, we can declare a string as follows.

string name;
		

Here name is a variable of string data type. To initialize a string, we simply assign a string literal to it.

string name = "Alice";
		

We can simply use it just like any other variable. The following line will print "Alice".

Console.WriteLine(name);
		

We can also create string type variable from character array. The string constructor can take a character array type of argument to initialize a string.

char[] nameArray = {'A', 'l', 'i', 'c', 'e'};
string name = new string(nameArray);
		

	var message = "Hello " + "World";
	Console.WriteLine(message);
			

	string name = "Alice";
	name = "Bob";
			

// 1. This will print "World" in the next line.
Console.WriteLine("Hello\nWorld");

// Output
/*
Hello
World
*/

// 2. This will create a tab space.
Console.WriteLine("Hello\tWorld");

// Output -
// Hello 	World

// 3. This will allow to use double quotes (") in a string literal (Normally we can't use this character because it indicates the start or end of string literal).
Console.WriteLine("\"Hello World\"");

// Output - 
// "Hello Word"

// 4. This will allow us to use backward slash (\) in a string literal (Normally we can't use this character because it indicates the start of an escape character in a string literal)

Console.WriteLine("D:\\Projects\\csharp\\Program.cs");

// Output - D:\Projects\csharp\Program.cs
			

var message = @"Hello Alice,
	
Good morning!

Your files have been saved to this location.
\shared\alice

Thanks.";

Console.WriteLine(message);

/* This will print the following output

Hello Alice,

Good Morning!

Your files have been saved to this location.
\shared\alice

Thanks.

*/
			

There are couple of ways in which we can manipulate string. Let's see those.

var name = "Alice";

var greeting = String.Format("Hello {0}, {1}!", name, "good morning");

Console.WriteLine(greeting);
			

var name = "Alice";
var greet = "good morning";

var greeting = $"Hello {name}, {greet}!";

Console.WriteLine(greeting);
			

var num = 12;
Console.WriteLine($"Square of { num } = { num * num }");
			

Here are some of the commonly used string methods in C#.

• Substring : It is used to get sub-string from a given string.

  
  var text = "Hello World";
  
  var sub_text = text.Substring(6, 5);
  
  Console.WriteLine(sub_text);
  
  // Output : World
  				

• ToUpper : It is used to convert the string into upper case letters.

  
  var text = "Hello World";
  Console.WriteLine(text.ToUpper());
  
  // Output : HELLO WORLD
  				

• ToLower : It is used to convert the string into lower case letters.

  
  var text = "Hello World";
  Console.WriteLine(text.ToLower());
  
  // Output : hello world
  				

• Trim : It is used to remove the spaces before first character and after last character of a string.

  
  var text = "    Hello World         ";
  Console.WriteLine(text.Trim());
  
  // Output : Hello World
  				

• Split : It is used to split a string into a string array based on a specific delimiter present in the string. The Split method takes a parameter called delimiter which is used to specify the splitting point within the string.

  
  var csv = "Alice,Bob,Chris,Dave,Eric,Fred";
  
  var names = csv.Split(','); 
  
  for( var i = 0; i < names.Length; i++)
  {
  	Console.WriteLine(names);
  }
  
  /* Output
  
  Alice
  Bob
  Chris
  Dave
  Eric
  Fred
  
  */
  				

• Contains : It is used to check whether a string contains a given substring or not.

  
  var greet = "Hello World";
  
  if(greet.Contains("World"))
  {
  	Console.WriteLine("World is a substring of {0}", greet);
  }
  				

• Replace : It is used to replace a part of string with another string.

  
  var greet = "Hello World";
  
  var newGreet = greet.Replace("World", "Team");
  
  Console.WriteLine(newGreet);
  
  // Output : Hello Team
  				

• IndexOf : It returns the index of the first occurrence of a specified character or string.

  
  var greet = "Hello Alice. Welcome";
  
  var index = greet.IndexOf("el");
  
  Console.WriteLine(index);
  
  // Output
  
  1
  				

• LastIndexOf : It returns the index of the last occurrence of a specified character or string.

  
  var greet = "Hello Alice. Welcome";
  
  var index = greet.LastIndexOf("el");
  
  Console.WriteLine(index);
  
  // Output
  
  14
  				

Here is the complete code below showing all different methods of string manipulations as described above.

Run this code

using System;

class Program
{
	static void Main(string[] args)
	{
		Console.WriteLine("-- Strings --");
		Console.WriteLine("");
		
		Console.WriteLine("-- Simple String --");
		Console.WriteLine("");
		
		string name = "Alice";
		Console.WriteLine(name);
		
		Console.WriteLine("");
		Console.WriteLine("-- String from char array --");
		Console.WriteLine("");
		
		char[] nameArray = {'A', 'l', 'i', 'c', 'e'};
		name = new string(nameArray);
		Console.WriteLine(name);
		
		Console.WriteLine("");
		Console.WriteLine("-- String Concatenation --");
		Console.WriteLine("");
		
		var message = "Hello " + "World";
		Console.WriteLine(message);
		
		Console.WriteLine("");
		Console.WriteLine("-- Escape characters --");
		Console.WriteLine("");
		
		Console.WriteLine("Hello\nWorld");
		Console.WriteLine("Hello\tWorld");
		Console.WriteLine("\"Hello World\"");
		Console.WriteLine("D:\\Projects\\csharp\\Program.cs");
		
		Console.WriteLine("");
		Console.WriteLine("-- Verbatim --");
		Console.WriteLine("");
		
		message = @"Hello Alice,
	
Good morning!

Your files have been saved to this location.
\shared\alice

Thanks.";

		Console.WriteLine(message);
		
		Console.WriteLine("");
		Console.WriteLine("-- String Interpolations --");
		Console.WriteLine("");
		
		name = "Alice";
		var greeting = String.Format("Hello {0}, {1}!", name, "good morning");
		Console.WriteLine(greeting);
		
		name = "Alice";
		var greet = "good morning";
		greeting = $"Hello {name}, {greet}!";
		Console.WriteLine(greeting);
		
		var num = 12;
		Console.WriteLine($"Square of { num } = { num * num }");
		
		Console.WriteLine("");
		Console.WriteLine("-- Other string methods --");
		Console.WriteLine("");
		
		var text = "Hello World";
		Console.WriteLine($"text = {text}");
		Console.WriteLine($"text.Substring(6, 5) : {text.Substring(6, 5)}");
		Console.WriteLine($"text.ToUpper() : {text.ToUpper()}");
		Console.WriteLine($"text.ToLower() : {text.ToLower()}");
		
		Console.WriteLine("");
		text = "    Hello World         ";
		Console.WriteLine($"text = {text}");
		Console.WriteLine($"text.Trim() : {text.Trim()}");
		
		var csv = "Alice,Bob,Chris,Dave,Eric,Fred";
		Console.WriteLine($"csv = {csv}");
		var names = csv.Split(','); 
		Console.WriteLine("csv.Split(\",\")");
		for( var i = 0; i < names.Length; i++)
		{
			Console.WriteLine(names[i]);
		}
		
		Console.WriteLine("");
		text = "Hello World";
		Console.WriteLine($"text = {text}");
		Console.WriteLine($"text.Contains(\"World\") : {text.Contains("World")}");
		
		Console.WriteLine($"text.Replace(\"World\", \"Team\") : {text.Replace("World", "Team")}");
		
		Console.WriteLine("");
		greet = "Hello Alice. Welcome!";
		Console.WriteLine($"greet = {greet}");
		Console.WriteLine($"greet.IndexOf(\"el\") : {greet.IndexOf("el")}");
		Console.WriteLine($"greet.LastIndexOf(\"el\") : {greet.LastIndexOf("el")}");
		
		Console.Write("Press any key to continue...");
		Console.ReadKey(true);
	}
}