The difference between String.Empty, string= "" and null

String.Empty is a static constant of the string class;

String.Empty and string= "" are not very different, because the internal implementation of String.Empty is:

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publicstaticreadonlystringEmpty;//这就是String.Empty 那是只读的String类的成员，也是string的变量的默认值是什么呢？//String的构造函数staticString(){    Empty = "";//Empty就是他""    WhitespaceChars = newchar[] {        ‘\t‘, ‘\n‘, ‘\v‘, ‘\f‘, ‘\r‘, ‘ ‘, ‘\x0085‘, ‘\x00a0‘, ‘?‘, ‘ ‘, ‘ ‘, ‘ ‘, ‘ ‘, ‘?‘, ‘?‘, ‘?‘,        ‘?‘, ‘?‘, ‘ ‘, ‘?‘, ‘‘, ‘\u2028‘, ‘\u2029‘, ‘　‘, ‘‘     };}

　　

Look at the code again:

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strings1 = "";string s2 = string.Empty;if(s1 == s2)<br>{    Console.WriteLine("一模一样！");}   // 结果都是TrueConsole.WriteLine("".Equals(string.Empty));Console.WriteLine(object.ReferenceEquals(string.Empty, ""));

Since String.Empty and string= "" also need to occupy memory space, why is it recommended to use String.Empty first?

String. Empty just lets the code read, preventing the code from making ambiguity, such as saying:

string s = "";   string s = ""; It's hard to see whether it's an empty string or a space character.

If a string is judged to be empty, use the

if (S==string.empty) and if (s== "") are the same efficiency, but the most efficient way to do this is if (s.length==0)

String. IsNullOrEmpty's internal implementation method:

publicstatic boolIsNullOrEmpty(stringvalue)<br>{<br>    if(value != null)    {        return(value.Length == 0);    }    returntrue;}

String str=null indicates that STR does not point to any object.

The difference between String.Empty, string= "" and null