我如何创建.NET财产的委托？ [英] How do I create a delegate for a .NET property?

问题描述

我想创建一个委托（作为测试）为：

I am trying to create a delegate (as a test) for:

Public Overridable ReadOnly Property PropertyName() As String

我的直观的尝试宣告委托是这样的：

My intuitive attempt was declaring the delegate like this:

Public Delegate Function Test() As String

和实例是这样的：

Dim t As Test = AddressOf e.PropertyName

但是，这引发错误：

But this throws the error:

方法公众可重写只读属性属性名（）作为
  串不具有一个签名
  与代表代表兼容
  功能测试（）作为字符串'。

Method 'Public Overridable ReadOnly Property PropertyName() As String' does not have a signature compatible with delegate 'Delegate Function Test() As String'.

，因为我正在处理我尝试这样一个属性：

So because I was dealing with a property I tried this:

Public Delegate Property Test() As String

不过，这将引发编译错误。

But this throws a compiler error.

所以，问题是，我怎么做一个委托财产？

So the question is, how do I make a delegate for a property?

请参阅此链接：

http://peisker.net/dotnet/propertydelegates.htm

推荐答案

重新使用AddressOf问题 - 如果你知道在编译时的道具名称，你可以（在C＃中，至少）使用匿名法/λ

Re the problem using AddressOf - if you know the prop-name at compile time, you can (in C#, at least) use an anon-method / lambda:

Test t = delegate { return e.PropertyName; }; // C# 2.0
Test t = () => e.PropertyName; // C# 3.0

我不是一个VB的专家，但反射索赔，这是一样的：

I'm not a VB expert, but reflector claims this is the same as:

Dim t As Test = Function 
    Return e.PropertyName
End Function

运作的？

---

原来的答复：

您创建的属性代表们 Delegate.CreateDelegate ;这可以是开放式的任何实例，固定单个实例 - 并可以为getter或setter;我给C的一个例子＃...

You create delegates for properties with Delegate.CreateDelegate; this can be open for any instance of the type, of fixed for a single instance - and can be for getter or setter; I'll give an example in C#...

using System;
using System.Reflection;
class Foo
{
    public string Bar { get; set; }
}
class Program
{
    static void Main()
    {
        PropertyInfo prop = typeof(Foo).GetProperty("Bar");
        Foo foo = new Foo();

        // create an open "getter" delegate
        Func<Foo, string> getForAnyFoo = (Func<Foo, string>)
            Delegate.CreateDelegate(typeof(Func<Foo, string>), null,
                prop.GetGetMethod());

        Func<string> getForFixedFoo = (Func<string>)
            Delegate.CreateDelegate(typeof(Func<string>), foo,
                prop.GetGetMethod());

        Action<Foo,string> setForAnyFoo = (Action<Foo,string>)
            Delegate.CreateDelegate(typeof(Action<Foo, string>), null,
                prop.GetSetMethod());

        Action<string> setForFixedFoo = (Action<string>)
            Delegate.CreateDelegate(typeof(Action<string>), foo,
                prop.GetSetMethod());

        setForAnyFoo(foo, "abc");
        Console.WriteLine(getForAnyFoo(foo));
        setForFixedFoo("def");
        Console.WriteLine(getForFixedFoo());
    }
}

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