c# | isnullorhitespace()方法

原文:https://www . geeksforgeeks . org/c-sharp-isnullorhitespace-method/

在 C# 中， 是一个字符串方法。用于检查指定的字符串是*空还是只包含空格字符。如果一个字符串没有被赋值或者被显式赋值为 null，那么它将为 null。***

语法:

public static bool IsNullOrWhiteSpace(String str)

说明:该方法将采用类型为系统的参数。字符串并且这个方法将返回一个布尔值。如果方法的参数列表为空或字符串。空，或者只包含空白字符，则返回真，否则返回假。

例:

Input : str  = null         // initialize by null value
        String.IsNullOrWhiteSpace(str)
Output: True

Input : str  = " "  // initialize by whitespace
        String.IsNullOrWhiteSpace(str)
Output: True

程序:演示 IsNullOrWhiteSpace()方法的工作原理:

// C# program to illustrate 
// IsNullOrWhiteSpace() Method
using System;
class Geeks {

    // Main Method
    public static void Main(string[] args)
    {
        string s1 = null;

        // for null value always return true
        bool b1 = String.IsNullOrWhiteSpace(s1);
        Console.WriteLine(b1);

        string s2 = " ";

        // for whitespace value always return true
        bool b2 = String.IsNullOrWhiteSpace(s2);
        Console.WriteLine(b2);

        string s4 = " \n ";

        // for new line value return true
        bool b4 = String.IsNullOrWhiteSpace(s4);
        Console.WriteLine(b4);

        string s5 = "\t";

        // for tab value return true
        bool b5 = String.IsNullOrWhiteSpace(s5);
        Console.WriteLine(b5);

        string s6 = "\r";

        // for carriage Return value return true
        bool b6 = String.IsNullOrWhiteSpace(s6);
        Console.WriteLine(b6);

        string s7 = "GFG";

        // for s7 it return False
        bool b7 = String.IsNullOrWhiteSpace(s7);
        Console.WriteLine(b7);
    }
}

Output:

True
True
True
True
True
False

注:isnullorhitespace()方法有一个备选代码如下:

return String.IsNullOrEmpty(str) || str.Trim().Length == 0;

程序:演示 IsNullOrEmpty()方法的替代方案

// C# program to illustrate the 
// similar code for IsNullOrWhiteSpace()
using System;
class Geeks {

    // similar code to 
    // IsNullOrWhiteSpace()
    public static bool check(string str)
    {
        return(String.IsNullOrEmpty(str) || 
              str.Trim().Length == 0) ? true : false;
    }

    // Main Method
    public static void Main(string[] args)
    {
        string s1 = "GeeksforGeeks";
        string s2 = " "; 
        string s3 = null;
        string s4 = " \n ";

        bool b1 = check(s1);
        bool b2 = check(s2);
        bool b3 = check(s3);
        bool b4 = check(s4);

        // To display result
        Console.WriteLine(b1);
        Console.WriteLine(b2);
        Console.WriteLine(b3);
        Console.WriteLine(b4);
    }
}

输出:

False
True
True
True

参考:T2

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