Differences between indexof and indexofany

A substring is a substring or character contained in a string. In the String class, common methods for locating substrings and characters include IndexOf/LastIndexOf and IndexOfAny/LastIndexOfAny. The following describes in detail.
1. IndexOf/LastIndexOf
The IndexOf method is used to search for the first occurrence of a specific character or substring in a string. This method is case sensitive and starts from the first character of the string and starts with 0. If the string does not contain this character or substring,-1 is returned. The following is a common heavy load method.

(1) Positioning characters:

Int IndexOf (char value)

Int IndexOf (char value, int startIndex)

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

(2) locate the substring:

Int IndexOf (string value)

Int IndexOf (string value, int startIndex)

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

In the above overload form, the parameter meanings are as follows:

Value: a character or substring of a given digit.

StartIndex: the actual position of the Start search in the total string.

Count: the number of characters from the start position in the total string.

The following code searches for the first occurrence location of the character 'l' in "Hello.

Code 4-7 use IndexOf to find the first occurrence location of a character: 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 specific character or substring in a string. Its legal meaning and return values are the same as IndexOf and will not be repeated.

2. IndexOfAny/LastIndexOfAny
The IndexOfAny method is similar to IndexOf. The difference is that it can search for the first position of any character in a string that appears in a character array. Similarly, this method is case sensitive and starts from the first character of a string and starts with 0. If the string does not contain this character or substring,-1 is returned. There are three common IndexOfAny reloads:

(1) int IndexOfAny (char [] anyOf );

(2) int IndexOfAny (char [] anyOf, int startIndex );

(3) int IndexOfAny (char [] anyOf, int startIndex, int count ).

In the above overload form, the parameter meanings are as follows:

(1) anyOf: A String Array of characters to be determined. The method returns the position where any character in the array appears for the first time.

(2) startIndex: the actual position where the search starts from the original string.

(3) count: number of characters searched from the start position in the original string.

In the following example, find the first and last occurrence location of the character 'l' in "Hello.

Code 4-8 Use IndexOfAny to find the first and last occurrence location of the 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 position of any character in a character array.