String.IsNullOrEmpty(String) String.IsNullOrEmpty(String) String.IsNullOrEmpty(String) String.IsNullOrEmpty(String) Method

Definición

Indica si el valor de la cadena especificada es null o una cadena vacía ("").Indicates whether the specified string is null or an empty string ("").

public:
 static bool IsNullOrEmpty(System::String ^ value);
public static bool IsNullOrEmpty (string value);
static member IsNullOrEmpty : string -> bool
Public Shared Function IsNullOrEmpty (value As String) As Boolean

Parámetros

value
String String String String

Cadena que se va a comprobar.The string to test.

Devoluciones

true si el parámetro value es null o una cadena vacía (""); en caso contrario, false.true if the value parameter is null or an empty string (""); otherwise, false.

Ejemplos

En el ejemplo siguiente se examinan las tres cadenas y determina si cada cadena tiene un valor, es una cadena vacía o es null.The following example examines three strings and determines whether each string has a value, is an empty string, or is null.

using namespace System;
String^ Test( String^ s )
{
   if (String::IsNullOrEmpty(s))
      return "is null or empty";
   else
      return String::Format( "(\"{0}\") is neither null nor empty", s );
}

int main()
{
   String^ s1 = "abcd";
   String^ s2 = "";
   String^ s3 = nullptr;
   Console::WriteLine( "String s1 {0}.", Test( s1 ) );
   Console::WriteLine( "String s2 {0}.", Test( s2 ) );
   Console::WriteLine( "String s3 {0}.", Test( s3 ) );
}
// 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.
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";
    else
        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.
Class Sample
   Public Shared Sub Main()
      Dim s1 As String = "abcd"
      Dim s2 As String = ""
      Dim s3 As String = Nothing
      
      Console.WriteLine("String s1 {0}.", Test(s1))
      Console.WriteLine("String s2 {0}.", Test(s2))
      Console.WriteLine("String s3 {0}.", Test(s3))
   End Sub
   
   Public Shared Function Test(s As String) As String
      If String.IsNullOrEmpty(s) Then
         Return "is null or empty"
      Else
         Return String.Format("(""{0}"") is neither null nor empty", s)
      End If
   End Function 
End Class  
' 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.

Comentarios

IsNullOrEmpty es un método de conveniencia que le permite probar simultáneamente si un String es null o su valor es String.Empty.IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is null or its value is String.Empty. Es equivalente al código siguiente:It is equivalent to the following code:

result = s == nullptr || s == String::Empty;
result = s == null || s == String.Empty;
result = s Is Nothing OrElse s = String.Empty

Puede usar el IsNullOrWhiteSpace método para comprobar si una cadena es null, su valor es String.Empty, o consta únicamente de caracteres de espacio en blanco.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.

¿Qué es una cadena null?What is a null string?

Una cadena es null si no se ha asignado un valor (en C++ y Visual Basic) o si explícitamente se ha asignado un valor de null.A string is null if it has not been assigned a value (in C++ and Visual Basic) or if it has explicitly been assigned a value of null. Aunque el formatos compuestos característica puede controlar correctamente una cadena nula, como muestra el siguiente ejemplo, al intentar llamar a uno si sus miembros produce un NullReferenceException.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 namespace System;

void main()
{
   String^ s;
  
   Console::WriteLine("The value of the string is '{0}'", s);

   try {
      Console::WriteLine("String length is {0}", s->Length);
   }
   catch (NullReferenceException^ e) {
      Console::WriteLine(e->Message);
   }   
}
// The example displays the following output:
//     The value of the string is ''
//     Object reference not set to an instance of an object.
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) {
         Console.WriteLine(e.Message);
      }
   }
}
// The example displays the following output:
//     The value of the string is ''
//     Object reference not set to an instance of an object.
Module Example
   Public Sub Main()
      Dim s As String

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

      Try 
         Console.WriteLine("String length is {0}", s.Length)
      Catch e As NullReferenceException
         Console.WriteLine(e.Message)
      End Try   
   End Sub
End Module
' The example displays the following output:
'     The value of the string is ''
'     Object reference not set to an instance of an object.

¿Qué es una cadena vacía?What is an empty string?

Una cadena está vacía si se asigna explícitamente una cadena vacía ("") o String.Empty.A string is empty if it is explicitly assigned an empty string ("") or String.Empty. Una cadena vacía tiene un Length de 0.An empty string has a Length of 0. En el ejemplo siguiente se crea una cadena vacía y se muestra su valor y su longitud.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.      
String s = "";
Console.WriteLine("The length of '{0}' is {1}.", s, s.Length);
// The example displays the following output:
//       The length of '' is 0.      
Dim s As String = ""
Console.WriteLine("The length of '{0}' is {1}.", s, s.Length)
' The example displays the following output:
'        The length of '' is 0.      

Se aplica a

Consulte también: