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String.IsNullOrEmpty Method

Silverlight

Updated: January 2011

Indicates whether the specified string is Nothing or an Empty string.

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

'Declaration
Public Shared Function IsNullOrEmpty ( _
	value As String _
) As Boolean

Parameters

value: Type: System.String
The string to test.

Return Value

Type: System.Boolean
true if the value parameter is Nothing or an empty string (""); otherwise, false.

Remarks

IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is Nothing or its value is Empty. It is equivalent to the following code:


result = s Is Nothing OrElse s = String.Empty

Examples

The following code example determines whether each of three strings has a value, is an empty string or is Nothing.


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.