IsNullOrEmpty Method

String.IsNullOrEmpty Method (String)


Indicates whether the specified string is null or an Empty string.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

public static bool IsNullOrEmpty(
	string value


Type: System.String

The string to test.

Return Value

Type: System.Boolean

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

IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is null or its value is Empty. It is equivalent to the following code:

result = s == null || s == String.Empty;

You can use the IsNullOrWhiteSpace method to test whether a string is null, its value is String.Empty, or it consists only of white-space characters.

A string is null if it has not been assigned a value (in C++ and Visual Basic) or if has explicitly been assigned a value of null. Although the composite formatting feature can gracefully handle a null string, as the following example shows, attempting to call one if its members throws a NullReferenceException.

using System;

public class Example
   public static void Main()
      String s = null;

      Console.WriteLine("The value of the string is '{0}'", s);

      try {
         Console.WriteLine("String length is {0}", s.Length);
      catch (NullReferenceException e) {
// The example displays the following output:
//     The value of the string is ''
//     Object reference not set to an instance of an object.

A string is empty if it is explicitly assigned an empty string ("") or String.Empty. An empty string has a Length of 0. The following example creates an empty string and displays its value and its length.

String s = "";
Console.WriteLine("The length of '{0}' is {1}.", s, s.Length);
// The example displays the following output:
//       The length of '' is 0.      

The following example examines three strings and determines whether each string has a value, is an empty string, or is null.

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)) 
        return "is null or empty";
        return String.Format("(\"{0}\") is neither null nor empty", s);
// The example displays the following output:
//       String s1 ("abcd") is neither null nor empty.
//       String s2 is null or empty.
//       String s3 is null or empty.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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