Author : HASSAN MD TAREQ | Updated : 2021/03/22

String syntax

// Empty string
var emptyText = String.Empty;  // zero-length string ""

// Literal string
var sampleText = "This is a string";

// Verbatim string: use @
var path = @"c:\test\foo.txt";  // rather than "c:\\test\\foo.txt"

// Interpolation
var x = 10;
var sampleTextByInterpolation = $"Value of x is {x}";

Split

/*
public string[] Split(separator, StringSplitOptions options)

Seperator => Char: ' ', String: " ", Char[], String[]
if Seperator is null or empty => white-space characters are assumed to be the delimiters

Enum StringSplitOptions: None/RemoveEmptyEntries            
StringSplitOptions.None : returned array will contain String.Empty ("") elements        
StringSplitOptions.RemoveEmptyEntries : returned array will not contain String.Empty ("") elements    
*/
var foo = "..."
var words = foo.Split(' ');  // seperator char
var words = foo.Split(",")   // seperator string

char[] delimiterChars = { ' ', ',', '.', '\t' };  // seperator char array
var words = foo.Split(delimiterChars);

string[] stringSeparators  = { ";", "." };          // seperator string array
var words = foo.Split(stringSeparators , StringSplitOptions.RemoveEmptyEntries);

string theString = "Some Very Large String Here";
var array = theString.Split(new [] { ' ' }, 2); // return at most 2 parts

Split details

var substrings = Regex.Split(input, pattern);

Regex regex = new Regex("-"); // Split on hyphens
var substrings = regex.Split("plum--pear");

/*
The Regex.Split methods are similar to the String.Split(Char[]) method, 
except that Regex.Split splits the string at a delimiter determined by a regular expression instead of a set of characters.
*/

See: Splitting String with RegEx

Join

/*
String.Join<T>(String, IEnumerable<T>);
String.Join<T>(String, Enumerable.Where<T>(lambda));
public static string Join (string separator, string[] value);
public static string Join (string separator, params object[] values);
public static string Join (string separator, string[] value, int startIndex, int count);

If separator is null, an empty string (String.Empty) is used instead. 
If any member of values is null, an empty string is used instead.
*/
var result = String.Join("|", 1, 2, 3);
var foo = new string[] {"bar", "baz"}
var result = String.Join("|", foo);
var result = String.Join("|", foo, 1, 2);

See: String.Join Method

String constructor

// Create a string from a character array
char[] chars = { 'w', 'o', 'r', 'l', 'd' };
string textFromCharArray = new string(chars);

// Create a string that consists of a character repeated 20 times.
string textWithSameCharMultipleTimes = new string('c', 20);

Empty check

String.IsNullOrEmpty(String); // static method
String.IsNullOrWhiteSpace(String); // static method

Readonly indexer

// String class has read only indexer
string str = "test";  
char x = str[2];  // x = 's'; 

Substring

Substring(startIndex); // up to end
Substring(startIndex, endIndex);

String[] pairs = { "Color1=red", "Color2=green", "Color3=blue", "Title=Code Repository" };
foreach (var pair in pairs) {

    int position = pair.IndexOf("=");
    if (position < 0) {
        continue;
    }
        
    var pre = pair.Substring(0, position);
    var post = pair.Substring(position + 1);
}   

See: String.Substring Method

Replace

/*
public string Replace (char oldChar, char newChar);
public string Replace (string oldValue, string newValue); // If newValue is null, all occurrences of oldValue are removed.
*/
String str = "1 2 3 4 5 6 7 8 9";
var foo = str.Replace(' ', ',')  // "1,2,3,4,5,6,7,8,9"

string errString = "This docment uses 3 other docments to docment the docmentation";
string correctString = errString.Replace("docment", "document");

// static and instance methods
Regex.Replace(string[], pattern, replaceWith);  // Regex.Replace(arr, @",", String.Empty);
Regex.Replace(overloads);  

Contains

public bool Contains (string value);

See: String.IndexOf Method

Char to String

// interpolation
char ch = 'x';
string str = $"{ch}";

// string constructor
string str = new string(new char[] { 'x' });

// ToString()
char ch = 'x';
var str = ch.ToString();

// when char is int val
var val = 120;
string str = Char.ConvertFromUtf32(val);  // x

String to Char

string str = "Hello";
char[] characters = str.ToCharArray();

// readonly indexer of string
var str = "hovermind";
var firstChar = str[0];  // h

Char Array to String

// string constructor
var charArray = new char[] { 'a', 'b', 'c' };
var str = new String(charArray);
Console.WriteLine(str);

var charArray = new char[] { 'a', 'b', 'c' };
var str = String.Join(" ", charArray);
Console.WriteLine(str);  // "a b c"

String to Char Array

// string is char array
var str = "abcd";
foreach(var ch in str){
	Console.WriteLine(ch);
}

// ToCharArray()
var str = "abcd";
var chars = str.ToCharArray();
foreach(var ch in chars){
	Console.WriteLine(ch);
}

// read only indexer of string
for(var i = 0; i < str.Length; i++) {
	var ch = str[i];
	Console.WriteLine(ch);
}

Array to String

var str = String.Join(" ", new char[] { 'a', 'b', 'c' });
Console.WriteLine(str);  // "a b c"

str = String.Join(" ", 'a', 'b', 'c');
Console.WriteLine(str);  // "a b c"

str = String.Join(" ", new string[] { "hover", "mind" });
Console.WriteLine(str);  // "hover mind"

str = String.Join(" ", "hover", "mind");
Console.WriteLine(str);  // "hover mind"

str = String.Join("|", 1, 2, 3);
Console.WriteLine(str);  // "1|2|3"

String to Word Array

var words = str.Split(seperator, StringSplitOptions options)  // seperator => Char: ' ' / String: " " / Char[] / String[]
/*
if separator is null or "" => deault (white-space characters) will be used
StringSplitOptions.None => returned array contains both empty and non-empty items
StringSplitOptions.RemoveEmptyEntries => returned array contains only non-empty items
when using String[] as seperator =>  must use StringSplitOptions
*/

var str = "ab cd ef";
var words = str.Split(' ');                            // seperator: char
var words = str.Split(new char[] { ' ' });             // seperator: char array  => method signature: Split(Char[])
var words = str.Split(" ");                            // seperator: string
// string array as seperators => method signature: Split(Char[], StringSplitOptions)
var words = str.Split(new string[] { " ", "|" }, StringSplitOptions.None);   // when using string array => must use StringSplitOptions

foreach(var word in words){
	Console.WriteLine(word);
}

String to List

List<string> words = myString.Split(" ").ToList()

List to String

//String.Join(string separator,  IEnumerable<T> collection);
List<string> words = new List<string> { "hover", "mind" };
var str = String.Join(" ",  words);
Console.WriteLine(str);

Dictionary to String

string str = string.Join(";", myDict.Select(kv => kv.Key + "=" + kv.Value).ToArray());

String to Dictionary

var dict = text.Split(new[] {';'}, StringSplitOptions.RemoveEmptyEntries)
               .Select(part => part.Split('='))
               .ToDictionary(split => split[0], split => split[1]);

Binary Digits as String

string binaryString = Convert.ToString(n, 2); // "110011010111"
int value = Convert.ToInt32("11001", 2)