C# | IsNullOrWhiteSpace() Method

In C#, IsNullOrWhiteSpace() is a string method. It is used to check whether the specified string is null or contains only white-space characters. A string will be null if it has not been assigned a value or has explicitly been assigned a value of null.

Syntax:

public static bool IsNullOrWhiteSpace(String str)  

Explanation: This method will take a parameter which is of type System.String and this method will return a boolean value. If the method’s parameter list is null or String.Empty, or only contains white-space characters then return True otherwise return False.

Example:

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

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

Program: To demonstrate the working of the IsNullOrWhiteSpace() Method :

// 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

Note: There is a alternative code of IsNullOrWhiteSpace() method as follows:

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

Program: To demonstrate IsNullOrEmpty() method’s alternative

// 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);
    }
}

Output:

False
True
True
True

Reference: https://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace