String.IsNullOrEmpty Method
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Updated: January 2011
Indicates whether the specified string is nulla null reference (Nothing in Visual Basic) or an Empty string.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared Function IsNullOrEmpty ( _
value As String _
) As Boolean
public static bool IsNullOrEmpty(
string value
)
Parameters
- value
Type: System.String
The string to test.
Return Value
Type: System.Boolean
true if the value parameter is nulla null reference (Nothing in Visual Basic) or an empty string (""); otherwise, false.
Remarks
IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is nulla null reference (Nothing in Visual Basic) or its value is Empty. It is equivalent to the following code:
result = s Is Nothing OrElse s = String.Empty
result = s == null || s == String.Empty;
Examples
The following code example determines whether each of three strings has a value, is an empty string or is nulla null reference (Nothing in Visual Basic).
Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim s1 As String = "abcd"
Dim s2 As String = ""
Dim s3 As String = Nothing
outputBlock.Text += String.Format("String s1 {0}.", Test(s1)) & vbCrLf
outputBlock.Text += String.Format("String s2 {0}.", Test(s2)) & vbCrLf
outputBlock.Text += String.Format("String s3 {0}.", Test(s3)) & vbCrLf
End Sub
Public Shared Function Test(ByVal s As String) As String
If String.IsNullOrEmpty(s) Then
Return "is null or empty"
Else
Return String.Format("(""{0}"") is not null or empty", s)
End If
End Function
End Class
' 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.
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";
else
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.
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
Change History
Date |
History |
Reason |
|---|---|---|
January 2011 |
Expanded the Remarks section. |
Customer feedback. |