C# index of usage (reprint)

Find the position where the specified character or string first appears in the string, return the first index value, such as :

str1.IndexOf("字")； //查找“字”在str1中的索引值（位置）
str1.IndexOf("字串")；//查找“字串”的第一个字符在str1中的索引值（位置）
str1.IndexOf("字",start,end)；//从str1第start+1个字符起，查找end个字符，查找“字”在字符串STR1中的位置[从第一个字符算起]注意:start+end不能大于str1的长度

The indexof parameter is string, find the position where the parameter string first appears in the string and return that position. For example, string s="0123dfdfdf"; int i=s.indexof("df"); then i==4. Returns -1 if not found.

If you need a more powerful string parsing function, you should use the Regex class and use regular expressions to match strings.

indexof(): Position characters and strings from front to back in the string; all return values ​​refer to the absolute position in the string, if empty, it is - 1

string test="asdfjsdfjgkfasdsfsgfhgjgfjgdddd";
test.indexof(’d’) =2          //从前向后 定位 d 第一次出现的位置
test.indexof(’d’,5,2)=6         //从前向后 定位 d 从第5 位开始查，查2位，即 从第5位到第7位；

lastindexof(): Position characters and strings from back to front in the string;
Usage is exactly the same as indexof().

Introduced below IndexOfAny ||lastindexofany

They accept a character array as a variable, other methods are the same as above, and return the earliest subscript position of any character in the array

As follows :

char[] bbv={’s’,’c’,’b’};
string abc = "acsdfgdfgchacscdsad";
Response.Write(abc.IndexOfAny(bbv))=1
Response.Write(abc.IndexOfAny(bbv, 5))=9
Response.Write(abc.IndexOfAny(bbv, 5, 3))=9

lastindexofany Same as above.

substring() Usage

string a="aadsfdjkfgklfdglfd"

a.substring(5) //Intercept all strings starting from the fifth digit

a.substring(0,5) //Intercept all strings from the 0th to the 5th.

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