判断字符串为空有好几种方法:
% a( n7 S7 K9 y; D7 J8 e5 {方法一: 代码如下:% b, t: }. O1 p2 P* y: R" O
- static void Main(string[] args)
- {
- string str = "";
-
- if (str == "")
- {
- Console.WriteLine("a is empty"); ;
- }
-
- Console.ReadKey();
- }
运行结果:a is empty 3 I5 q b, P; ]2 @) W, j5 B$ y- h
" M! {% K1 K4 m* a! Z这样针对str = ""也是可以的,但是大多数场景是在方法的 入口处判空,这个字符串有可能是null,也有可能是" ",甚至是"\n",上面这种判空方法显示不能覆盖这么多场景;
- m, d$ v$ p2 C E方法二 :这时候IsNullOrEmpty就横空出世了,针对字符串值为string.Empty、str2 = ""、null,都可以用 Y7 R# _9 c; G" [* G% |' e
- static void Main(string[] args)
- {
- string str1 = string.Empty;
-
- if (string.IsNullOrEmpty(str1))
- {
- Console.WriteLine("str1 is empty"); ;
- }
-
- string str2 = "";
-
- if (string.IsNullOrEmpty(str2))
- {
- Console.WriteLine("str2 is empty"); ;
- }
-
- string str3 = null;
-
- if (string.IsNullOrEmpty(str3))
- {
- Console.WriteLine("str3 is empty"); ;
- }
-
- Console.ReadKey();
- }
运行结果如下:
, I ^/ M$ [ ]; }; u
( V. ^9 _+ {9 [/ q8 w) v方法三 :但是IsNullOrEmpty在字符串为" ","\n","\t",时候就无能为力了,为了覆盖这些场景,高手们一般判空使用方法IsNullOrWhiteSpace( v) _& r: i, V; P
- static void Main(string[] args)
- {
- string str1 = string.Empty;
-
- if (string.IsNullOrWhiteSpace(str1))
- {
- Console.WriteLine("str1 is empty"); ;
- }
-
- string str2 = "";
-
- if (string.IsNullOrWhiteSpace(str2))
- {
- Console.WriteLine("str2 is empty"); ;
- }
-
- string str3 = null;
-
- if (string.IsNullOrWhiteSpace(str3))
- {
- Console.WriteLine("str3 is empty"); ;
- }
-
- string str4 = " ";
-
- if (string.IsNullOrWhiteSpace(str4))
- {
- Console.WriteLine("str4 is empty"); ;
- }
-
- string str5 = "\n";
-
- if (string.IsNullOrWhiteSpace(str5))
- {
- Console.WriteLine("str5 is empty"); ;
- }
-
- string str6 = "\t";
-
- if (string.IsNullOrWhiteSpace(str6))
- {
- Console.WriteLine("str6 is empty"); ;
- }
- Console.ReadKey();
- }
运行结果:
2 ]: ]& {9 O: V' ~ I
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