判断字符串为空有好几种方法:
方法一: 代码如下:
static void Main(string[] args){string str = "";if (str == ""){Console.WriteLine("a is empty"); ;}Console.ReadKey();}
运行结果:a is empty
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;
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
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:
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
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: