String.IsNullOrEmpty官方示例

// This example demonstrates the String.IsNullOrEmpty() method
using System;
  
class Sample 
{
    public static void Main() 
    {
    string s1 = "abcd";
    string s2 = "";
    string s3 = null;
  
    Console.WriteLine("String s1 {0}.", Test(s1));
    Console.WriteLine("String s2 {0}.", Test(s2));
    Console.WriteLine("String s3 {0}.", Test(s3));
    }
  
    public static String Test(string s)
    {
    if (String.IsNullOrEmpty(s) == true) 
        return "is null or empty";
    else
        return String.Format("(\"{0}\") is not null or empty", s);
    }
}
/*
This example produces the following results:
  
String s1 ("abcd") is not null or empty.
String s2 is null or empty.
String s3 is null or empty.
  
*/

String类提供的这个IsNullOrEmpty方法十分的优雅，英语就是graceful。String的话一般都会有""和null两种情况，如果自己写，用if(s=="" || s==Null)就不太美妙了。