Attribute.Match(Object) Método
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Cuando se invalida en una clase derivada, devuelve un valor que indica si esta instancia es igual a un objeto especificado.
public:
virtual bool Match(System::Object ^ obj);public virtual bool Match (object? obj);public virtual bool Match (object obj);abstract member Match : obj -> bool
override this.Match : obj -> boolPublic Overridable Function Match (obj As Object) As BooleanParámetros
Devoluciones
Es true si esta instancia es igual a obj; en caso contrario, es false.
Comentarios
Este método determina si uno Attribute es igual a otro. Su implementación predeterminada es la misma Equalsque , que determina si dos atributos son del mismo tipo y tienen los mismos valores de campo.
En general, el Equals método está pensado para realizar una prueba estándar para la igualdad de referencia o valor. Puede invalidar el Match método cuando desee realizar una comparación personalizada para la igualdad basada en algunos criterios distintos de que dos instancias de atributo tengan el mismo tipo y tengan valores idénticos. Por ejemplo, puede invalidar el Match método para comparar atributos en los escenarios siguientes:
Un atributo incluye un campo de bits y se consideran dos instancias de atributo iguales si se establece un bit determinado. Por ejemplo, un
NumericDisplayatributo podría incluir un campo de bits que indica qué formatos numéricos (como binario, octal, decimal y hexadecimal) admite un cliente. El método invalidado Match podría considerar dos instancias iguales si admiten el mismo formato numérico.Un atributo incluye varios campos que contienen el mismo tipo de información o contiene una matriz en la que los valores pueden estar en cualquier orden. Por ejemplo, un
Authoratributo podría incluir varios campos para los nombres de autor. El método invalidado Match puede considerar dos instancias iguales si tienen los mismos autores, independientemente de si cada campo es igual al campo correspondiente.
Ejemplo
En el ejemplo siguiente se muestra el uso de para crear un método de comparación personalizado para los valores de Match atributo. Si define un AuthorsAttribute objeto que contiene internamente un List<String> objeto que almacena los nombres de los autores. Dado que los nombres pueden producirse en cualquier orden de la lista, invalida el Match método para comparar nombres de autor independientemente de su posición en la lista. Observe el Equals método , que realiza una prueba para la igualdad de valores, devuelve resultados diferentes del Match método .
using System;
using System.Collections.Generic;
using System.Reflection;
// A custom attribute to allow multiple authors per method.
[AttributeUsage(AttributeTargets.Method)]
public class AuthorsAttribute : Attribute
{
protected List<string> _authors;
public AuthorsAttribute(params string[] names)
{
_authors = new List<string>(names);
}
public List<string> Authors
{
get { return _authors; }
}
// Determine if the object is a match to this one.
public override bool Match(object obj)
{
// Return false if obj is null or not an AuthorsAttribute.
AuthorsAttribute authors2 = obj as AuthorsAttribute;
if (authors2 == null) return false;
// Return true if obj and this instance are the same object reference.
if (Object.ReferenceEquals(this, authors2))
return true;
// Return false if obj and this instance have different numbers of authors
if (_authors.Count != authors2._authors.Count)
return false;
bool matches = false;
foreach (var author in _authors)
{
for (int ctr = 0; ctr < authors2._authors.Count; ctr++)
{
if (author == authors2._authors[ctr])
{
matches = true;
break;
}
if (ctr == authors2._authors.Count)
{
matches = false;
}
}
}
return matches;
}
public override string ToString()
{
string retval = "";
for (int ctr = 0; ctr < _authors.Count; ctr++)
{
retval += $"{_authors[ctr]}{(ctr < _authors.Count - 1 ? ", " : String.Empty)}";
}
if (retval.Trim().Length == 0)
{
return "<unknown>";
}
return retval;
}
}
// Add some authors to methods of a class.
public class TestClass {
[Authors("Leo Tolstoy", "John Milton")]
public void Method1()
{}
[Authors("Anonymous")]
public void Method2()
{}
[Authors("Leo Tolstoy", "John Milton", "Nathaniel Hawthorne")]
public void Method3()
{}
[Authors("John Milton", "Leo Tolstoy")]
public void Method4()
{}
}
class Example
{
static void Main()
{
// Get the type for TestClass to access its metadata.
Type clsType = typeof(TestClass);
// Iterate through each method of the class.
AuthorsAttribute authors = null;
foreach(var method in clsType.GetMethods())
{
// Check each method for the Authors attribute.
AuthorsAttribute authAttr = (AuthorsAttribute) Attribute.GetCustomAttribute(method,
typeof(AuthorsAttribute));
if (authAttr != null)
{
// Display the authors.
Console.WriteLine($"{clsType.Name}.{method.Name} was authored by {authAttr}.");
// Select Method1's authors as the basis for comparison.
if (method.Name == "Method1")
{
authors = authAttr;
Console.WriteLine();
continue;
}
// Compare first authors with the authors of this method.
if (authors.Match(authAttr))
{
Console.WriteLine("TestClass.Method1 was also authored by the same team.");
}
// Perform an equality comparison of the two attributes.
Console.WriteLine($"{authors} {(authors.Equals(authAttr) ? "=" : "<>")} {authAttr}");
Console.WriteLine();
}
}
}
}
// The example displays the following output:
// TestClass.Method1 was authored by Leo Tolstoy, John Milton.
//
// TestClass.Method2 was authored by Anonymous.
// Leo Tolstoy, John Milton <> Anonymous
//
// TestClass.Method3 was authored by Leo Tolstoy, John Milton, Nathaniel Hawthorne.
// Leo Tolstoy, John Milton <> Leo Tolstoy, John Milton, Nathaniel Hawthorne
//
// TestClass.Method4 was authored by John Milton, Leo Tolstoy.
// TestClass.Method1 was also authored by the same team.
// Leo Tolstoy, John Milton <> John Milton, Leo Tolstoy
open System
// A custom attribute to allow multiple authors per method.
[<AttributeUsage(AttributeTargets.Method); AllowNullLiteral>]
type AuthorsAttribute([<ParamArray>] names: string []) =
inherit Attribute()
member val Authors = ResizeArray names
// Determine if the object is a match to this one.
override this.Match(obj) =
match obj with
| :? AuthorsAttribute as authors2 ->
// Return true if obj and this instance are the same object reference.
if Object.ReferenceEquals(this, authors2) then true
// Return false if obj and this instance have different numbers of authors
elif this.Authors.Count <> authors2.Authors.Count then false
else
let authors1 = this.Authors |> set
let authors2 = this.Authors |> set
authors1 = authors2
| _ ->
// Return false if obj is null or not an AuthorsAttribute.
false
override this.ToString() =
let retval = String.Join(", ", this.Authors)
if retval.Trim().Length = 0 then
"<unknown>"
else
retval
// Add some authors to methods of a class.
type TestClass() =
[<Authors("Leo Tolstoy", "John Milton")>]
member _.Method1() = ()
[<Authors "Anonymous">]
member _.Method2() = ()
[<Authors("Leo Tolstoy", "John Milton", "Nathaniel Hawthorne")>]
member _.Method3() = ()
[<Authors("John Milton", "Leo Tolstoy")>]
member _.Method4() = ()
// Get the type for TestClass to access its metadata.
let clsType = typeof<TestClass>
// Iterate through each method of the class.
let mutable authors = null
for method in clsType.GetMethods() do
// Check each method for the Authors attribute.
let authAttr =
Attribute.GetCustomAttribute(method, typeof<AuthorsAttribute>)
:?> AuthorsAttribute
if authAttr <> null then
// Display the authors.
printfn $"{clsType.Name}.{method.Name} was authored by {authAttr}."
// Select Method1's authors as the basis for comparison.
if method.Name = "Method1" then
authors <- authAttr
printfn ""
else
// Compare first authors with the authors of this method.
if authors.Match authAttr then
printfn "TestClass.Method1 was also authored by the same team."
// Perform an equality comparison of the two attributes.
printfn $"""{authors} {if authors.Equals(authAttr) then "=" else "<>"} {authAttr}"""
printfn ""
// The example displays the following output:
// TestClass.Method1 was authored by Leo Tolstoy, John Milton.
//
// TestClass.Method2 was authored by Anonymous.
// Leo Tolstoy, John Milton <> Anonymous
//
// TestClass.Method3 was authored by Leo Tolstoy, John Milton, Nathaniel Hawthorne.
// Leo Tolstoy, John Milton <> Leo Tolstoy, John Milton, Nathaniel Hawthorne
//
// TestClass.Method4 was authored by John Milton, Leo Tolstoy.
// TestClass.Method1 was also authored by the same team.
// Leo Tolstoy, John Milton <> John Milton, Leo Tolstoy
Imports System.Collections.Generic
Imports System.Reflection
' A custom attribute to allow multiple authors per method.
<AttributeUsage(AttributeTargets.Method)> _
Public Class AuthorsAttribute : Inherits Attribute
Protected _authors As List(Of String)
Public Sub New(paramarray names As String())
_authors = New List(Of string)(names)
End Sub
Public ReadOnly Property Authors As List(Of String)
Get
Return _authors
End Get
End Property
' Determine if the object is a match to this one.
Public Overrides Function Match(obj As Object) As Boolean
' Return false if obj is null or not an AuthorsAttribute.
Dim authors2 As AuthorsAttribute = DirectCast(obj, AuthorsAttribute)
If authors2 Is Nothing Then Return False
' Return true if obj and this instance are the same object reference.
If Object.ReferenceEquals(Me, authors2) Then Return True
' Return false if obj and this instance have different numbers of authors
If _authors.Count <> authors2._authors.Count Then Return False
Dim matches As Boolean = False
For Each author in _authors
For ctr As Integer = 0 To authors2._authors.Count - 1
If author = authors2._authors(ctr) Then
matches = True
Exit For
End If
If ctr = authors2._authors.Count Then matches = False
Next
Next
Return matches
End Function
Public Overrides Function ToString() As String
Dim retval As String = ""
For ctr As Integer = 0 To _authors.Count -1
retval += $"{_authors(ctr)}{If(ctr < _authors.Count - 1, ", ", String.Empty)}"
Next
If retval.Trim().Length = 0 Then Return "<unknown>"
Return retval
End Function
End Class
' Add some authors to methods of a class.
Public Class TestClass
<Authors("Leo Tolstoy", "John Milton")>
Public sub Method1()
End sub
<Authors("Anonymous")>
Public Sub Method2()
End Sub
<Authors("Leo Tolstoy", "John Milton", "Nathaniel Hawthorne")>
Public Sub Method3()
End Sub
<Authors("John Milton", "Leo Tolstoy")>
Public Sub Method4()
End Sub
End Class
Public Module Example
Public Sub Main()
' Get the type for TestClass to access its metadata.
Dim clsType As Type = GetType(TestClass)
' Iterate through each method of the class.
Dim authors As AuthorsAttribute = Nothing
For Each method In clsType.GetMethods()
' Check each method for the Authors attribute.
Dim authAttr As AuthorsAttribute = DirectCast(Attribute.GetCustomAttribute(method,
GetType(AuthorsAttribute)), AuthorsAttribute)
If authAttr IsNot Nothing Then
' Display the authors.
Console.WriteLine($"{clsType.Name}.{method.Name} was authored by {authAttr}.")
' Select Method1's authors as the basis for comparison.
If method.Name = "Method1" Then
authors = authAttr
Console.WriteLine()
Continue For
End If
' Compare first authors with the authors of this method.
If authors.Match(authAttr) Then
Console.WriteLine("TestClass.Method1 was also authored by the same team.")
End If
' Perform an equality comparison of the two attributes.
Console.WriteLine($"{authors} {If(authors.Equals(authAttr), "=", "<>")} {authAttr}")
Console.WriteLine()
End If
Next
End Sub
End Module
' The example displays the following output:
// TestClass.Method1 was authored by Leo Tolstoy, John Milton.
//
// TestClass.Method2 was authored by Anonymous.
// Leo Tolstoy, John Milton <> Anonymous
//
// TestClass.Method3 was authored by Leo Tolstoy, John Milton, Nathaniel Hawthorne.
// Leo Tolstoy, John Milton <> Leo Tolstoy, John Milton, Nathaniel Hawthorne
//
// TestClass.Method4 was authored by John Milton, Leo Tolstoy.
// TestClass.Method1 was also authored by the same team.
// Leo Tolstoy, John Milton <> John Milton, Leo Tolstoy