IndexOf and IndexOfAny The difference introduction _ Practical Skills

Locating a substring is the search for a string that contains a substring or a character. In the string class, the common methods for locating substrings and characters include Indexof/lastindexof and Indexofany/lastindexofany, which are described in detail below.
1. Indexof/lastindexof
The IndexOf method is used to search for the first occurrence of a particular character or substring in a string, which is case-sensitive and counts 0 from the first character of the string. Returns-1 if the string does not contain this character or substring. The commonly used overloaded forms are shown below.

(1) Positioning character:

int IndexOf (char value)

int IndexOf (char value, int startIndex)

int IndexOf (char value, int startIndex, int count)

(2) Set seat string:

int IndexOf (string value)

int IndexOf (string value, int startIndex)

int IndexOf (string value, int startIndex, int count)

In the above overloaded form, the parameter meaning is as follows:

Value: The character or substring to be positioned.

StartIndex: The fact that the search begins in the total string.

Count: The number of characters that are searched from the start position in the total string.

The following code looks for the first occurrence of the character ' L ' in "Hello".

Code 4-7 using IndexOf to find the first occurrence of a character position: Default.aspx.cs

1. String s= "Hello";

2. int I = S.indexof (' l ')); 2

Similar to IndexOf, LastIndexOf is used to search for the last occurrence of a particular character or substring in a string, and its method definition and return values are the same as indexof and no longer repeat.

2. Indexofany/lastindexofany
The IndexOfAny method function is similar to indexof, except that it can search for the first occurrence of any character in a character array that appears in a string. Similarly, the method is case-sensitive and starts with a 0 count from the first character of the string. Returns-1 if the string does not contain this character or substring. There are 3 types of commonly used IndexOfAny overload forms:

(1) int indexofany (char[]anyof);

(2) int indexofany (char[]anyof, int startIndex);

(3) int indexofany (char[]anyof, int startIndex, int count).

In the above overloaded form, the parameter meaning is as follows:

(1) anyof: An array of characters to be positioned, and the method returns the first occurrence of any character in the array.

(2) StartIndex: The fact that the search begins in the original string.

(3) Count: The number of characters to search from the start position in the original string.

The following example looks for the first and last occurrences of the character ' L ' in "Hello".

Code 4-8 using IndexOfAny to find the first and last occurrence of a substring: Default.aspx.cs

1. String s = "Hello";

2. char[] anyof={' H ', ' e ', ' l '};

3. int i1 = S.indexofany (anyof)); 0

4. int i2 = S.lastindexofany (anyof)); 3

Similar to IndexOfAny, Lastindexofany is used to search for the last occurrence of any character in a character array that appears in a string.