String Constructor (new string)Create strings with char arrays and repeated characters using the string constructor.
This page was last reviewed on Nov 20, 2022.
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.
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.
Detail The string constructor is an ideal way to convert a char array to a string.
Convert Char Array, String
Tip To create a new string, you usually should just modify an existing string or use a string literal.
String Literal
using System; class Program { static void Main() { // 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.
Detail This is much simpler than using PadRight or PadLeft methods to create repeated characters.
PadRight, PadLeft
using System; class Program { static void Main() { // 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.
Detail This string constructor is the equivalent of Substring, but acts on char arrays.
using System; class Program { static void Main() { // 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
Constructors. We look at the 8 string constructors in the .NET Framework. You can see that 5 of the constructors are unsafe. Unsafe code should usually be avoided.
unsafe public String(char*); public String(char[]); unsafe public String(sbyte*); public String(char, int); unsafe public String(char*, int, int); public String(char[], int, int); unsafe public String(sbyte*, int, int); unsafe public String(sbyte*, int, int, Encoding);
Notes. This page doesn't demonstrate the unsafe constructors, as your code should avoid unsafe methods. You might need these 5 unsafe methods for DLL interop.
Tip There is no difference between calling "new String" and "new string". The uppercase first letter makes no difference.
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.
Optimization, repeat chars. We can optimize the string constructor that repeats characters N times to a string literal. In a benchmark, the literal is faster (it is already generated).
A summary. 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.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Nov 20, 2022 (simplify).
© 2007-2023 Sam Allen.