String.substring（int32,int32）(php|c#)

public String Substring(int startIndex,int length)

起始位置从0开始，然后截取长度

如：判断文件的后缀名是否为gif

string filename=File.name.ToString();

if(filename.Substring(filename.length-3,3) =="gif")

 

php里的substring()

<?php
echo substr('abcdef', 1);     // bcdef
echo substr('abcdef', 1, 3);  // bcd
echo substr('abcdef', 0, 4);  // abcd
echo substr('abcdef', 0, 8);  // abcdef
echo substr('abcdef', -1, 1); // f

// Accessing single characters in a string
// can also be achived using "curly braces"
$string = 'abcdef';
echo $string{0};                 // a
echo $string{3};                 // d
echo $string{strlen($string)-1}; // f


?>

<?php
$rest = substr("abcdef", -1);    // returns "f"
$rest = substr("abcdef", -2);    // returns "ef"
$rest = substr("abcdef", -3, 1); // returns "d"


?>

<?php
$rest = substr("abcdef", 0, -1);  // returns "abcde"
$rest = substr("abcdef", 2, -1);  // returns "cde"
$rest = substr("abcdef", 4, -4);  // returns ""
$rest = substr("abcdef", -3, -1); // returns "de"
?>