String

System

Class String

Represents text as a sequence of UTF-16 code units. The String class is immutable, meaning that once an object of the String class is created, the value of that string cannot be changed. Although the value of a string object cannot be changed, you can still create new string objects to represent modified versions of an existing string.

Namespace: System

Assembly: System.Runtime.dll

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Members

Constructors

public String(char* value);

Initializes a new instance of the String class to the specified Unicode character array.

public String(char c, int count);

Initializes a new instance of the String class to the specified Unicode character, and repeats the character a specified number of times.

Properties

public int Length { get; }

Gets the number of characters in the current String object.

Methods

public static String Concat(String str0, String str1);

Concatenates the string representation of the specified objects.

string firstName = "John";
string lastName = "Doe";
string fullName = String.Concat(firstName, " ", lastName);
// fullName is now "John Doe"

public static int Compare(String strA, String strB);

Compares two strings and returns an integer that indicates whether the first string precedes, is equal to, or follows the second string in sort order.

string s1 = "apple";
string s2 = "banana";
int comparison = String.Compare(s1, s2);
if (comparison < 0)
{
    Console.WriteLine($"'{s1}' comes before '{s2}'");
}

public bool Contains(String value);

Determines whether the specified string occurs within this string.

string message = "Hello, World!";
bool hasWorld = message.Contains("World"); // true

public int IndexOf(String value);

Returns the zero-based index of the first occurrence of the specified string within the current string.

string text = "This is a sample text.";
int index = text.IndexOf("sample"); // 10

public String ToLower();

Converts this string to lowercase.

string mixedCase = "MiXeD CaSe";
string lowerCase = mixedCase.ToLower(); // "mixed case"

public String ToUpper();

Converts this string to uppercase.

string mixedCase = "MiXeD CaSe";
string upperCase = mixedCase.ToUpper(); // "MIXED CASE"

public String Trim();

Removes all leading and trailing white space characters from the current String object.

string spacedString = "   Trim me   ";
string trimmed = spacedString.Trim(); // "Trim me"

public String Replace(String oldValue, String newValue);

Replaces all occurrences of a specified string in this instance with another specified string.

string original = "Hello planet, hello universe!";
string replaced = original.Replace("hello", "hi"); // "Hi planet, hi universe!"

public Char[] ToCharArray();

Copies the characters into a new character array.

string word = "Code";
char[] chars = word.ToCharArray(); // ['C', 'o', 'd', 'e']

Operators

public static bool operator ==(String a, String b);

Compares two string objects for equality.

public static bool operator !=(String a, String b);

Compares two string objects for inequality.