# String.IsNullOrEmpty(String) Método

## 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

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

#### Devoluciones

Boolean

`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 tres cadenas y se 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.
``````
``````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));

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 útil 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;
``````
``````bool TestForNullOrEmpty(string s)
{
bool result;
result = s == null || s == string.Empty;
return result;
}

string s1 = null;
string s2 = "";
Console.WriteLine(TestForNullOrEmpty(s1));
Console.WriteLine(TestForNullOrEmpty(s2));

// The example displays the following output:
//    True
//    True
``````
``````result = s Is Nothing OrElse s = String.Empty
``````

Puede usar el IsNullOrWhiteSpace método para probar si una cadena es `null` , su valor es String.Empty o solo consta 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 nula?What is a null string?

Una cadena es `null` si no se le ha asignado un valor (en C++ y Visual Basic) o si se ha asignado explícitamente 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 la característica de formato compuesto puede controlar correctamente una cadena nula, como se muestra en el ejemplo siguiente, se intenta llamar a una si sus miembros inician una excepción 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.
``````
``````  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 le 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 valor 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.
``````