C# - String Constructor (new string)

String constructor. Usually a string constructor call is not needed. But the C# language has many string constructors. These create strings from characters and arrays.

One possible use for a string constructor is creating a string containing one char repeated many times. Another is converting a char array into a string.

Constructor

Char array example. To begin, we show how to create a string from a char array. The string constructor in C# is useful for creating strings from various data sources.

Part 1 We create a 3-element char array. It is at first empty, but we assign 3 characters to its memory.

char Array

Part 2 Here we create a string with a string constructor from an existing char array. The string "abc" results from a 3-char array.

Tip The string constructor is an ideal way to convert a char array to a string.

Convert Char Array

Tip 2 To create a new string, you usually should just modify an existing string or use a string literal.

String Literal

using System; // Part 1: create char array. char[] charArray = new char[3]; charArray[0] = 'a'; charArray[1] = 'b'; charArray[2] = 'c'; // Part 2: create string from array. string exampleString = new string(charArray); Console.WriteLine(exampleString); Console.WriteLine(exampleString == "abc");

abc True

Repeated chars. Suppose we want to create a whitespace string with a space repeated 100 times. This is easy with the string constructor—no large string literal is needed.

Here We repeat the letter "A" 10 times. The resulting string can be used like any other in a C# program.

using System; // Create new string of repeated characters. string exampleString = new string('a', 10); Console.WriteLine(exampleString); Console.WriteLine(exampleString == "aaaaaaaaaa");

aaaaaaaaaa True

Char array, range. Suppose we have a char array, but want to create a string from just part of it. We can use another string constructor and specify and offset or a length.

Here We start at index 0, and continue until we have taken 3 chars. We turn the first 3 chars of the array into a string.

using System; // Create new string from range of characters in array. char[] charArray = new char[6]; charArray[0] = 'a'; charArray[1] = 'B'; charArray[2] = 'c'; charArray[3] = 'D'; charArray[4] = 'e'; charArray[5] = 'F'; string exampleString = new string(charArray, 0, 3); Console.WriteLine(exampleString); Console.WriteLine(exampleString == "aBc");

aBc True

Optimization. We can use the string constructors as an impressive optimization. Sometimes, we can entirely replace StringBuilder with a char array.

And This is most useful for sorting algorithms or other lower-level operations on strings in C# programs.

StringBuilder

Also We can optimize the string constructor that repeats characters N times to a string literal. In a benchmark, the literal is faster.

Benchmark

String constructors are occasionally useful. We used the 3 string constructors in C# that are not unsafe. And we found ways string conversions can be optimized.