本文整理匯總了VB.NET中System.Delegate.CreateDelegate方法的典型用法代碼示例。如果您正苦於以下問題:VB.NET Delegate.CreateDelegate方法的具體用法?VB.NET Delegate.CreateDelegate怎麽用?VB.NET Delegate.CreateDelegate使用的例子?那麽, 這裏精選的方法代碼示例或許可以為您提供幫助。您也可以進一步了解該方法所在類System.Delegate
的用法示例。
在下文中一共展示了Delegate.CreateDelegate方法的3個代碼示例,這些例子默認根據受歡迎程度排序。您可以為喜歡或者感覺有用的代碼點讚,您的評價將有助於係統推薦出更棒的VB.NET代碼示例。
示例1: Example
' 導入命名空間
Imports System.Reflection
Imports System.Security.Permissions
' Declare three delegate types for demonstrating the combinations
' of Shared versus instance methods and open versus closed
' delegates.
'
Public Delegate Sub D1(ByVal c As C, ByVal s As String)
Public Delegate Sub D2(ByVal s As String)
Public Delegate Sub D3()
' A sample class with an instance method and a Shared method.
'
Public Class C
Private id As Integer
Public Sub New(ByVal id As Integer)
Me.id = id
End Sub
Public Sub M1(ByVal s As String)
Console.WriteLine("Instance method M1 on C: id = {0}, s = {1}", _
Me.id, s)
End Sub
Public Shared Sub M2(ByVal s As String)
Console.WriteLine("Shared method M2 on C: s = {0}", s)
End Sub
End Class
Public Class Example
Public Shared Sub Main()
Dim c1 As New C(42)
' Get a MethodInfo for each method.
'
Dim mi1 As MethodInfo = GetType(C).GetMethod("M1", _
BindingFlags.Public Or BindingFlags.Instance)
Dim mi2 As MethodInfo = GetType(C).GetMethod("M2", _
BindingFlags.Public Or BindingFlags.Static)
Dim d1 As D1
Dim d2 As D2
Dim d3 As D3
Console.WriteLine(vbLf & "An instance method closed over C.")
' In this case, the delegate and the
' method must have the same list of argument types; use
' delegate type D2 with instance method M1.
'
Dim test As [Delegate] = _
[Delegate].CreateDelegate(GetType(D2), c1, mi1, False)
' Because False was specified for throwOnBindFailure
' in the call to CreateDelegate, the variable 'test'
' contains Nothing if the method fails to bind (for
' example, if mi1 happened to represent a method of
' some class other than C).
'
If test IsNot Nothing Then
d2 = CType(test, D2)
' The same instance of C is used every time the
' delegate is invoked.
d2("Hello, World!")
d2("Hi, Mom!")
End If
Console.WriteLine(vbLf & "An open instance method.")
' In this case, the delegate has one more
' argument than the instance method; this argument comes
' at the beginning, and represents the hidden instance
' argument of the instance method. Use delegate type D1
' with instance method M1.
'
d1 = CType([Delegate].CreateDelegate(GetType(D1), Nothing, mi1), D1)
' An instance of C must be passed in each time the
' delegate is invoked.
'
d1(c1, "Hello, World!")
d1(New C(5280), "Hi, Mom!")
Console.WriteLine(vbLf & "An open Shared method.")
' In this case, the delegate and the method must
' have the same list of argument types; use delegate type
' D2 with Shared method M2.
'
d2 = CType([Delegate].CreateDelegate(GetType(D2), Nothing, mi2), D2)
' No instances of C are involved, because this is a Shared
' method.
'
d2("Hello, World!")
d2("Hi, Mom!")
Console.WriteLine(vbLf & "A Shared method closed over the first argument (String).")
' The delegate must omit the first argument of the method.
' A string is passed as the firstArgument parameter, and
' the delegate is bound to this string. Use delegate type
' D3 with Shared method M2.
'
d3 = CType([Delegate].CreateDelegate(GetType(D3), "Hello, World!", mi2), D3)
' Each time the delegate is invoked, the same string is
' used.
d3()
End Sub
End Class
輸出:
An instance method closed over C. Instance method M1 on C: id = 42, s = Hello, World! Instance method M1 on C: id = 42, s = Hi, Mom! An open instance method. Instance method M1 on C: id = 42, s = Hello, World! Instance method M1 on C: id = 5280, s = Hi, Mom! An open Shared method. Shared method M2 on C: s = Hello, World! Shared method M2 on C: s = Hi, Mom! A Shared method closed over the first argument (String). Shared method M2 on C: s = Hello, World!
示例2: Base
' 導入命名空間
Imports System.Reflection
' Define two classes to use in the demonstration, a base class and
' a class that derives from it.
'
Public Class Base
End Class
Public Class Derived
Inherits Base
' Define a Shared method to use in the demonstration. The method
' takes an instance of Base and returns an instance of Derived.
' For the purposes of the demonstration, it is not necessary for
' the method to do anything useful.
'
Public Shared Function MyMethod(ByVal arg As Base) As Derived
Dim dummy As Base = arg
Return New Derived()
End Function
End Class
' Define a delegate that takes an instance of Derived and returns an
' instance of Base.
'
Public Delegate Function Example(ByVal arg As Derived) As Base
Module Test
Sub Main()
' The binding flags needed to retrieve MyMethod.
Dim flags As BindingFlags = _
BindingFlags.Public Or BindingFlags.Static
' Get a MethodInfo that represents MyMethod.
Dim minfo As MethodInfo = _
GetType(Derived).GetMethod("MyMethod", flags)
' Demonstrate contravariance of parameter types and covariance
' of return types by using the delegate Example to represent
' MyMethod. The delegate binds to the method because the
' parameter of the delegate is more restrictive than the
' parameter of the method (that is, the delegate accepts an
' instance of Derived, which can always be safely passed to
' a parameter of type Base), and the return type of MyMethod
' is more restrictive than the return type of Example (that
' is, the method returns an instance of Derived, which can
' always be safely cast to type Base).
'
Dim ex As Example = CType( _
[Delegate].CreateDelegate(GetType(Example), minfo), _
Example _
)
' Execute MyMethod using the delegate Example.
'
Dim b As Base = ex(New Derived())
End Sub
End Module
示例3: Example
' 導入命名空間
Imports System.Reflection
Imports System.Security.Permissions
' Declare a delegate type. The object of this code example
' is to show all the methods this delegate can bind to.
'
Public Delegate Sub D(ByVal c As C)
' Declare two sample classes, C and F. Class C has an ID
' property so instances can be identified.
'
Public Class C
Private _id As Integer
Public ReadOnly Property ID() As Integer
Get
Return _id
End Get
End Property
Public Sub New(ByVal newId As Integer)
Me._id = newId
End Sub
Public Sub M1(ByVal c As C)
Console.WriteLine("Instance method M1(c As C) on C: this.id = {0}, c.ID = {1}", _
Me.id, c.ID)
End Sub
Public Sub M2()
Console.WriteLine("Instance method M2() on C: this.id = {0}", Me.id)
End Sub
Public Shared Sub M3(ByVal c As C)
Console.WriteLine("Shared method M3(c As C) on C: c.ID = {0}", c.ID)
End Sub
Public Shared Sub M4(ByVal c1 As C, ByVal c2 As C)
Console.WriteLine("Shared method M4(c1 As C, c2 As C) on C: c1.ID = {0}, c2.ID = {1}", _
c1.ID, c2.ID)
End Sub
End Class
Public Class F
Public Sub M1(ByVal c As C)
Console.WriteLine("Instance method M1(c As C) on F: c.ID = {0}", c.ID)
End Sub
Public Shared Sub M3(ByVal c As C)
Console.WriteLine("Shared method M3(c As C) on F: c.ID = {0}", c.ID)
End Sub
Public Shared Sub M4(ByVal f As F, ByVal c As C)
Console.WriteLine("Shared method M4(f As F, c As C) on F: c.ID = {0}", c.ID)
End Sub
End Class
Public Class Example
Public Shared Sub Main()
Dim c1 As New C(42)
Dim c2 As New C(1491)
Dim f1 As New F()
Dim d As D
' Instance method with one argument of type C.
Dim cmi1 As MethodInfo = GetType(C).GetMethod("M1")
' Instance method with no arguments.
Dim cmi2 As MethodInfo = GetType(C).GetMethod("M2")
' Shared method with one argument of type C.
Dim cmi3 As MethodInfo = GetType(C).GetMethod("M3")
' Shared method with two arguments of type C.
Dim cmi4 As MethodInfo = GetType(C).GetMethod("M4")
' Instance method with one argument of type C.
Dim fmi1 As MethodInfo = GetType(F).GetMethod("M1")
' Shared method with one argument of type C.
Dim fmi3 As MethodInfo = GetType(F).GetMethod("M3")
' Shared method with an argument of type F and an
' argument of type C.
Dim fmi4 As MethodInfo = GetType(F).GetMethod("M4")
Console.WriteLine(vbLf & "An instance method on any type, with an argument of type C.")
' D can represent any instance method that exactly matches its
' signature. Methods on C and F are shown here.
'
d = CType([Delegate].CreateDelegate(GetType(D), c1, cmi1), D)
d(c2)
d = CType([Delegate].CreateDelegate(GetType(D), f1, fmi1), D)
d(c2)
Console.WriteLine(vbLf & "An instance method on C with no arguments.")
' D can represent an instance method on C that has no arguments;
' in this case, the argument of D represents the hidden first
' argument of any instance method. The delegate acts like a
' Shared method, and an instance of C must be passed each time
' it is invoked.
'
d = CType([Delegate].CreateDelegate(GetType(D), Nothing, cmi2), D)
d(c1)
Console.WriteLine(vbLf & "A Shared method on any type, with an argument of type C.")
' D can represent any Shared method with the same signature.
' Methods on F and C are shown here.
'
d = CType([Delegate].CreateDelegate(GetType(D), Nothing, cmi3), D)
d(c1)
d = CType([Delegate].CreateDelegate(GetType(D), Nothing, fmi3), D)
d(c1)
Console.WriteLine(vbLf & "A Shared method on any type, with an argument of")
Console.WriteLine(" that type and an argument of type C.")
' D can represent any Shared method with one argument of the
' type the method belongs and a second argument of type C.
' In this case, the method is closed over the instance of
' supplied for the its first argument, and acts like an instance
' method. Methods on F and C are shown here.
'
d = CType([Delegate].CreateDelegate(GetType(D), c1, cmi4), D)
d(c2)
Dim test As [Delegate] = _
[Delegate].CreateDelegate(GetType(D), f1, fmi4, false)
' This final example specifies False for throwOnBindFailure
' in the call to CreateDelegate, so the variable 'test'
' contains Nothing if the method fails to bind (for
' example, if fmi4 happened to represent a method of
' some class other than F).
'
If test IsNot Nothing Then
d = CType(test, D)
d(c2)
End If
End Sub
End Class
輸出:
An instance method on any type, with an argument of type C. Instance method M1(c As C) on C: this.id = 42, c.ID = 1491 Instance method M1(c As C) on F: c.ID = 1491 An instance method on C with no arguments. Instance method M2() on C: this.id = 42 A Shared method on any type, with an argument of type C. Shared method M3(c As C) on C: c.ID = 42 Shared method M3(c As C) on F: c.ID = 42 A Shared method on any type, with an argument of that type and an argument of type C. Shared method M4(c1 As C, c2 As C) on C: c1.ID = 42, c2.ID = 1491 Shared method M4(f As F, c As C) on F: c.ID = 1491