C# System.String API Reference

`String`

8 methods

Represents text as a sequence of UTF-16 code units. String is immutable and reference type.

String.Length -> int

Gets the number of characters in the current String object (UTF-16 code units).

Returns

int

Example

csharp

string s = "hello";
int len = s.Length;  // 5

String.Substring(int startIndex, int length) -> string

Retrieves a substring from this instance starting at startIndex with the specified length.

Parameters

Name	Type	Description
startIndex	int	Zero-based starting character position.
length	int	Number of characters to take.

Returns

string

Example

csharp

string s = "Hello, World";
string sub = s.Substring(7, 5);  // "World"

String.IndexOf(string value) -> int

Reports the zero-based index of the first occurrence of value, or -1 if not found.

Parameters

Name	Type	Description
value	string	String to seek.

Returns

int

Example

csharp

string s = "Hello, World";
int i = s.IndexOf("World");  // 7
int j = s.IndexOf("xyz");    // -1

String.Replace(string old, string new) -> string

Returns a new string in which all occurrences of old are replaced with new.

Parameters

Name	Type	Description
old	string	String to be replaced.
new	string	String to replace all occurrences of old.

Returns

string

Example

csharp

string s = "Hello, World";
string r = s.Replace("World", "C#");  // "Hello, C#"

String.Split(char[] separator) -> string[]

Splits the string into substrings based on the characters in separator.

Parameters

Name	Type	Description
separator	char[]	Character array that delimits substrings.

Returns

string[]

Example

csharp

string s = "a,b,c";
string[] parts = s.Split(',');
// parts == ["a", "b", "c"]

String.ToUpper() -> string

Returns a copy of this string converted to uppercase using the current culture's casing rules.

Returns

string

Example

csharp

string s = "hello";
string upper = s.ToUpper();  // "HELLO"

String.Trim() -> string

Removes all leading and trailing white-space characters from the current string.

Returns

string

Example

csharp

string s = "  hello  ";
string t = s.Trim();  // "hello"

String.Concat(string a, string b) -> string

Concatenates two specified string instances.

Parameters

Name	Type	Description
a	string	First string to concatenate.
b	string	Second string to concatenate.

Returns

string

Example

csharp

string r = string.Concat("Hello, ", "World");  // "Hello, World"

All references Next: System.Collections.Generic.List<T>