C# String - IsNullOrEmpty() Method

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The C# String IsNullOrEmpty() method is used to check whether the specified string is null or an empty string (" ").

A string considered to be null if it has not been assigned a value, while a string is empty if it is assigned only an empty pair of double quotes ("") or String.Empty().

Syntax

Following is the syntax of the C# string IsNullOrEmpty() method −

 public static bool IsNullOrEmpty (string? value); 

Parameters

This method accepts a string value as a parameter representing the string to be checked.

Return Value

This method returns true if the value parameter is null or an empty string (""); otherwise, false.

Example 1: Check Whether String is Empty

Following is a basic example of the IsNullOrEmpty() method to check whether string is empty or not −

 using System; class Program { static void Main() { string str = ""; bool res = string.IsNullOrEmpty(str); if (res == true) { Console.WriteLine("String is empty."); } else { Console.WriteLine("String is neither empty nor null."); } } } 

Output

Following is the output −

 String is empty. 

Example 2: Check Whether String is Null

Let's look at another example. Here, we use the IsNullOrEmpty() method to check string is null or not −

 using System; class Program { static void Main() { string str = null; bool res = string.IsNullOrEmpty(str); if (res == true) { Console.WriteLine("String is null"); } else { Console.WriteLine("String is not null."); } } } 

Output

Following is the output −

 String is null 

Example 3: Differentiate Between Null and Empty

In the following example, we differentiate between null and empty strings without using the IsNullOrEmpty method −

 using System; class Program { static void Main() { string str = null; if (str == null) { Console.WriteLine("String is null."); } else if (str == string.Empty) { Console.WriteLine("String is empty."); } else { Console.WriteLine("String is not null or empty."); } } } 

Output

Following is the output −

 String is null. 

Example 4: What If String is Neither Null nor Empty

The example below uses the IsNullOrEmpty() method to check if a string is empty or null. If the string is neither null nor empty, it will display false −

 using System; class Program { static void Main() { string str = "Hello TP"; bool res = string.IsNullOrEmpty(str); if(res == true){ Console.WriteLine("String is either Empty or Null"); } else{ Console.WriteLine("String is neither Empty nor Null"); Console.WriteLine("string value: {0}", str); } } } 

Output

Following is the output −

 String is neither Empty nor Null string value: Hello TP