IsNullOrEmpty Method

String.IsNullOrEmpty Method

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

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;

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

using System;

class Example
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
      string s1 = "abcd";
      string s2 = "";
      string s3 = null;

      outputBlock.Text += String.Format("String s1 {0}.", Test(s1)) + "\n";
      outputBlock.Text += String.Format("String s2 {0}.", Test(s2)) + "\n";
      outputBlock.Text += String.Format("String s3 {0}.", Test(s3)) + "\n";

   public static String Test(string s)
      if (String.IsNullOrEmpty(s))
         return "is null or empty";
         return String.Format("(\"{0}\") is not null or empty", s);
// The example displays the following output:
//       String s1 ("abcd") is not null or empty.
//       String s2 is null or empty.
//       String s3 is null or empty.

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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