dev-train-doc/csharp/06.string.md

字符串

string 类型是一种特殊的引用类型，每次操作都会生成一个新的副本进行操作。

属性

Length

获取当前字符串中字符的个数

string str = "hello world";
int len = str.Length; 

方法

Compare

静态方法，比较两个字符串的先后，返回值小于零，说明字符串A顺序在字符串B前面；返回零，说明两者顺序相同；大于零，说明字符串A顺序在字符串B后面

常用重载

• Compare(String? strA, String? strB)

• Compare(String? strA, String? strB, bool ignoreCase) //是否忽略大小写

• Compare(String? strA, String? strB, bool ignoreCase, CultureInfo? culture) //指定区域信息

string strA = "001";
string strB = "002";
int result = String.Compare(strA, strB);

Concat

静态方法，连接指定的字符串，并返回拼接后的字符串

常用重载

• Concat(params String?[] values)
• Concat(String? str0, String? str1)

string[] strs = new string[]{"a","b","c","d"};
string strNew = String.Concat(strs);

Copy

静态方法，复制指定的字符串

String.Copy("abcde")

Equals

静态方法，判断两个字符串是否相等

常用重载

• Equals(String? a, String? b)
• Equals(String? a, String? b, StringComparison comparisonType)用于指定比较用的排序规则和是否区分大小写

string str1 = "hello world";
string str2 = "Hello World";
if(string.Equals(str1, str2)
{
    ……
}

Join

静态方法，用指定的字符或字符串，连接多个字符串

常用重载

• Join(String? separator, IEnumerable values)
• Join(String? separator, params String?[] value)
• Join(char separator, params String?[] value)

string[] strs = new string[] { "a", "b", "c", "d" };
string strNew = string.Join(',',strs);

CompareTo

用于和指定的字符串做比较

string str1 = "Hello";
string str2 = "hello";
int result = str1.CompareTo(str2);

Contains

判断字符串是否包含指定字符或字符串

常用重载

• Contains(String value)
• Contains(char value)

string str = "hello world";
bool result = str.Contains('o');

EndsWith

判断字符串是否以指定的字符或字符串结尾

常用重载

• EndsWith(char value)
• EndsWith(String value)
• EndsWith(String value, bool ignoreCase, CultureInfo? culture)
• EndsWith(String value, StringComparison comparisonType)

string str = "hello world";
bool result = str.EndWith('o');

Equals

判断字符串是否与指定的字符串相等

常用重载

• Equals(String? value)
• Equals(String? value, StringComparison comparisonType)

string str = "hello world";
bool result = str.Equals("HELLO WORLD");

IndexOf

获取指定字符或字符串在字符串中首次出现的位置

常用重载

• IndexOf(String value, StringComparison comparisonType)
• IndexOf(String value, int startIndex, StringComparison comparisonType)
• IndexOf(String value, int startIndex, int count, StringComparison comparisonType)
• IndexOf(String value, int startIndex, int count)
• IndexOf(String value, int startIndex)
• IndexOf(String value)
• IndexOf(char value, StringComparison comparisonType)
• IndexOf(char value, int startIndex, int count)
• IndexOf(char value, int startIndex)
• IndexOf(char value)

string str = "hello world";
int result = str.Indexof('o');

LastIndexOf

获取指定字符或字符串在字符串中最后一次出现的位置

常用重载

• LastIndexOf(char value, int startIndex, int count)
• LastIndexOf(char value, int startIndex)
• LastIndexOf(String value, StringComparison comparisonType)
• LastIndexOf(String value, int startIndex, StringComparison comparisonType)
• LastIndexOf(char value)
• LastIndexOf(String value, int startIndex, int count)
• LastIndexOf(String value, int startIndex)
• LastIndexOf(String value)
• LastIndexOf(String value, int startIndex, int count, StringComparison comparisonType)
• LastIndexOfAny(char[] anyOf)
• LastIndexOfAny(char[] anyOf, int startIndex)
• LastIndexOfAny(char[] anyOf, int startIndex, int count)

string str = "hello world";
int result = str.LastIndexOf('o');

PadLeft

把字符串从左侧填充到指定的长度

常用重载

• PadLeft(int totalWidth) 用空格填充
• PadLeft(int totalWidth, char paddingChar) 用指定字符串填充

string str = "hello";
string str1 = str.PadLeft(10);

PadRight

把字符串从右侧填充到指定的长度

常用重载

• PadRight(int totalWidth) 用空格填充
• PadRight(int totalWidth, char paddingChar) 用指定字符串填充

string str = "hello";
string str1 = str.PadRight(10);

Remove

在字符串中从指定位置移除指定长度的字符串

常用重载

• Remove(int startIndex) 指定位置后面的字符串全部移除
• Remove(int startIndex, int count)

string str = "hello";
string str1 = str.Remove(2,1);

Replace

用指定的新字符串替换指定的老字符串

常用重载

• Replace(char oldChar, char newChar)
• Replace(String oldValue, String? newValue)
• Replace(String oldValue, String? newValue, bool ignoreCase, CultureInfo? culture)
• Replace(String oldValue, String? newValue, StringComparison comparisonType)

string str1 = "Hello World";
string str2 = str1.Replace("World","China");

Split

按照指定的字符将字符串拆分为数组

常用重载

• Split(String[]? separator, int count, StringSplitOptions options)
• Split(String? separator, int count, StringSplitOptions options = StringSplitOptions.None)
• Split(String[]? separator, StringSplitOptions options)
• Split(char[]? separator, int count, StringSplitOptions options)
• Split(String? separator, StringSplitOptions options = StringSplitOptions.None)
• Split(char[]? separator, StringSplitOptions options)
• Split(char separator, StringSplitOptions options = StringSplitOptions.None)
• Split(params char[]? separator)
• Split(char[]? separator, int count)、
• Split(char separator, int count, StringSplitOptions options = StringSplitOptions.None)

string str = "Hello World";
string[] strs = str.Split('');

StartsWith

判断字符串是否已指定的字符或字符串开头

常用重载

• StartsWith(char value)
• StartsWith(String value)
• StartsWith(String value, bool ignoreCase, CultureInfo? culture)
• StartsWith(String value, StringComparison comparisonType)

string str = "Hello World";
bool result = str.StartsWith('h');

Substring

从制定位置截取指定长度的字符串

常用重载

• Substring(int startIndex)
• Substring(int startIndex, int length)

string str = "Hello World";
string result = str.Substring(2,2);

ToLower

将字符串转换成小写形式

常用重载

• ToLower()
• ToLower(CultureInfo? culture)，用于指定区域性信息

string str = "HELLO WORLD";
string strNew = str.ToLower();

ToUpper

将字符串转化成大写形式

常用重载

• ToUpper()
• ToUpper(CultureInfo? culture)，用于指定区域性信息

string str = "hello world";
string strNew = str.ToUpper();

Trim

去掉字符串两端指定的字符

常用重载

• Trim()
• Trim(char trimChar)
• Trim(params char[]? trimChars)

string str = "  hello world  ";
string strNew = str.Trim();

TrimEnd

去掉字符串右端指定的字符

常用重载

• TrimEnd()
• TrimEnd(char trimChar)
• TrimEnd(params char[]? trimChars)

string str = "  hello world  ";
string strNew = str.TrimEnd();

TrimStart

去掉字符串左端指定的字符

常用重载

• TrimStart()
• TrimStart(char trimChar)
• TrimStart(params char[]? trimChars)

string str = "  hello world  ";
string strNew = str.TrimStart();