Array.Exists(T[], Predicate<T>) Array.Exists(T[], Predicate<T>) Array.Exists(T[], Predicate<T>) Array.Exists(T[], Predicate<T>) Method

Definición

Determina si la matriz especificada contiene elementos que coinciden con las condiciones definidas por el predicado especificado.Determines whether the specified array contains elements that match the conditions defined by the specified predicate.

public:
generic <typename T>
 static bool Exists(cli::array <T> ^ array, Predicate<T> ^ match);
public static bool Exists<T> (T[] array, Predicate<T> match);
static member Exists : 'T[] * Predicate<'T> -> bool
Public Shared Function Exists(Of T) (array As T(), match As Predicate(Of T)) As Boolean

Parámetros de tipo

T

Tipo de los elementos de la matriz.The type of the elements of the array.

Parámetros

array
T[]

Array unidimensional de base cero en la que se realizará la búsqueda.The one-dimensional, zero-based Array to search.

match
Predicate<T> Predicate<T> Predicate<T> Predicate<T>

Delegado Predicate<T> que define las condiciones de los elementos que se van a buscar.The Predicate<T> that defines the conditions of the elements to search for.

Devoluciones

true si array contiene uno o varios elementos que coinciden con las condiciones definidas por el predicado especificado; de lo contrario, false.true if array contains one or more elements that match the conditions defined by the specified predicate; otherwise, false.

Excepciones

array es null.array is null.

O bien-or- match es null.match is null.

Ejemplos

En el ejemplo siguiente se especifican las condiciones Exists de coincidencia para el método mediante expresiones lambda para comprobar si un planeta comienza con una letra determinada o si se encuentra el planeta en la matriz especificada.The following example specifies the match conditions for the Exists method using lambda expressions to check whether a planet starts with a given letter or whether the planet is found on the given array.

using System;

namespace Example
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] planets = { "Mercury", "Venus",
                "Earth", "Mars", "Jupiter",
                "Saturn", "Uranus", "Neptune" };

            Console.WriteLine("One or more planets begin with 'M': {0}",
                Array.Exists(planets, element => element.StartsWith("M")));

            Console.WriteLine("One or more planets begin with 'T': {0}",
                Array.Exists(planets, element => element.StartsWith("T")));

            Console.WriteLine("Is Pluto one of the planets? {0}",
                Array.Exists(planets, element => element == "Pluto"));
        }
    }
}
// The example displays the following output:
//       One or more planets begin with 'M': True
//       One or more planets begin with 'T': False
//       Is Pluto one of the planets? False
Module Example
    Public Sub Main()
        Dim planets() As String = {"Mercury", "Venus",
                                    "Earth", "Mars", "Jupiter",
                                    "Saturn", "Uranus", "Neptune"}

        Console.WriteLine("One or more planets begin with 'M': {0}",
            Array.Exists(planets, Function(element)
                                      Return element.StartsWith("M")
                                  End Function))

        Console.WriteLine("One or more planets begin with 'T': {0}",
            Array.Exists(planets, Function(element)
                                      Return element.StartsWith("T")
                                  End Function))

        Console.WriteLine("Is Pluto one of the planets? {0}",
            Array.Exists(planets, Function(element)
                                      Return element.Equals("Pluto")
                                  End Function))

    End Sub
End Module
' The example displays the following output:
'       One or more planets begin with 'M': True
'       One or more planets begin with 'T': False
'       Is Pluto one of the planets? False

En el ejemplo siguiente se Exists usa el método para indicar si los nombres de una matriz de cadenas comienzan con un carácter especificado.The following example uses the Exists method to indicate whether any names in a string array begin with a specified character. En el ejemplo se crea StringSearcher una instancia de un objeto pasando la cadena que se va a buscar a su constructor de clase.The example instantiates a StringSearcher object by passing the string to search for to its class constructor. El StringSearcher.StartsWith método tiene la misma firma que Predicate<T> el delegado.The StringSearcher.StartsWith method has same signature as the Predicate<T> delegate. Cuando se llama al true método,cadamiembrodelamatrizsepasaaldelegadohastaquedevuelveorecorreeniteracióntodosloselementosdelamatriz.ExistsWhen the Exists method is called, each member of the array is passed to the delegate until it returns true or iterates all the elements in the array.

using System;

public class Example
{
   public static void Main()
   {
      String[] names = { "Adam", "Adel", "Bridgette", "Carla",
                         "Charles", "Daniel", "Elaine", "Frances",
                         "George", "Gillian", "Henry", "Irving",
                         "James", "Janae", "Lawrence", "Miguel",
                         "Nicole", "Oliver", "Paula", "Robert",
                         "Stephen", "Thomas", "Vanessa",
                         "Veronica", "Wilberforce" };
      Char[] charsToFind = { 'A', 'K', 'W', 'Z' };

      foreach (var charToFind in charsToFind)
         Console.WriteLine("One or more names begin with '{0}': {1}",
                           charToFind,
                           Array.Exists(names, (new StringSearcher(charToFind)).StartsWith));
   }
}

public class StringSearcher
{
   Char firstChar;

   public StringSearcher(Char firstChar)
   {
      this.firstChar = Char.ToUpper(firstChar);
   }

   public bool StartsWith(String s)
   {
      if (String.IsNullOrEmpty(s)) return false;

      if(s.Substring(0, 1).ToUpper() == firstChar.ToString())
         return true;
      else
         return false;
   }
}
// The example displays the following output:
//       One or more names begin with 'A': True
//       One or more names begin with 'K': False
//       One or more names begin with 'W': True
//       One or more names begin with 'Z': False
Module Example
   Public Sub Main()
      Dim names() As String = { "Adam", "Adel", "Bridgette", "Carla",
                                "Charles", "Daniel", "Elaine", "Frances",
                                "George", "Gillian", "Henry", "Irving",
                                "James", "Janae", "Lawrence", "Miguel",
                                "Nicole", "Oliver", "Paula", "Robert",
                                "Stephen", "Thomas", "Vanessa",
                                "Veronica", "Wilberforce" }
      Dim charsToFind() As Char = { "A"c, "K"c, "W"c, "Z"c }
      
      For Each charToFind In charsToFind
         Console.WriteLine("One or more names begin with '{0}': {1}",
                           charToFind,
                           Array.Exists(names, AddressOf (New StringSearcher(charToFind)).StartsWith))
      Next
   End Sub
   
End Module

Public Class StringSearcher
   Dim firstChar As Char
   
   Public Sub New(firstChar As Char)
      Me.firstChar = Char.ToUpper(firstChar)
   End Sub
   
   Public Function StartsWith(s As String) As Boolean
      If String.IsNullOrEmpty(s) Then Return False
      
      If s.Substring(0, 1).ToUpper = firstChar Then
         Return True
      Else
         Return False
      End If
   End Function
End Class
' The example displays the following output:
'       One or more names begin with 'A': True
'       One or more names begin with 'K': False
'       One or more names begin with 'W': True
'       One or more names begin with 'Z': False

También puede utilizar una expresión lambda en lugar de definir explícitamente un método cuya firma se corresponda con la del delegado.You can also use a lambda expression rather than explicitly define a method whose signature corresponds to that of the delegate. En el ejemplo siguiente se StringSearcher reemplaza la clase StartsWith y su método por una expresión lambda.The following example replaces the StringSearcher class and its StartsWith method with a lambda expression.

using System;

public class Example
{
   public static void Main()
   {
      String[] names = { "Adam", "Adel", "Bridgette", "Carla",
                         "Charles", "Daniel", "Elaine", "Frances",
                         "George", "Gillian", "Henry", "Irving",
                         "James", "Janae", "Lawrence", "Miguel",
                         "Nicole", "Oliver", "Paula", "Robert",
                         "Stephen", "Thomas", "Vanessa",
                         "Veronica", "Wilberforce" };
      Char[] charsToFind = { 'A', 'K', 'W', 'Z' };

      foreach (var charToFind in charsToFind)
         Console.WriteLine("One or more names begin with '{0}': {1}",
                           charToFind,
                           Array.Exists(names,
                                        s => { if (String.IsNullOrEmpty(s))
                                                  return false;

                                               if (s.Substring(0, 1).ToUpper() == charToFind.ToString())
                                                  return true;
                                               else
                                                  return false;
                                             } ));
   }
}
// The example displays the following output:
//       One or more names begin with 'A': True
//       One or more names begin with 'K': False
//       One or more names begin with 'W': True
//       One or more names begin with 'Z': False
Module Example
   Public Sub Main()
      Dim names() As String = { "Adam", "Adel", "Bridgette", "Carla",
                                "Charles", "Daniel", "Elaine", "Frances",
                                "George", "Gillian", "Henry", "Irving",
                                "James", "Janae", "Lawrence", "Miguel",
                                "Nicole", "Oliver", "Paula", "Robert",
                                "Stephen", "Thomas", "Vanessa",
                                "Veronica", "Wilberforce" }
      Dim charsToFind() As Char = { "A"c, "K"c, "W"c, "Z"c }

      For Each charToFind In charsToFind
         Console.WriteLine("One or more names begin with '{0}': {1}",
                           charToFind,
                           Array.Exists(names, Function(s)
                                                  If String.IsNullOrEmpty(s) Then Return False

                                                  If s.Substring(0, 1).ToUpper = charToFind Then
                                                     Return True
                                                  Else
                                                     Return False
                                                  End If
                                               End Function ))
      Next
   End Sub
End Module
' The example displays the following output:
'       One or more names begin with 'A': True
'       One or more names begin with 'K': False
'       One or more names begin with 'W': True
'       One or more names begin with 'Z': False

Comentarios

Es un delegado de un método que devuelve true si el objeto que se pasa coincide con las condiciones definidas en el delegado. Predicate<T>The Predicate<T> is a delegate to a method that returns true if the object passed to it matches the conditions defined in the delegate. Los elementos de array se pasan individualmente a y Predicate<T>el procesamiento se detiene cuando se encuentra una coincidencia.The elements of array are individually passed to the Predicate<T>, and processing is stopped when a match is found.

Nota

En C# y Visual Basic, no es necesario crear el Predicate<T> delegado explícitamente.In C# and Visual Basic, it is not necessary to create the Predicate<T> delegate explicitly. Estos lenguajes deducen el delegado correcto del contexto y lo crean automáticamente.These languages infer the correct delegate from context and create it automatically.

Este método es una operación On(), donde n es el Length de array.This method is an O(n) operation, where n is the Length of array.

Se aplica a

Consulte también: