C#：返回给定对象和方法名称的委托
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C#: Return a delegate given an object and a method name
提问by Austin Salonen
Suppose I'm given an object and a string that holds a method name, how can I return a delegate to that method (of that method?) ?
假设我得到一个对象和一个包含方法名称的字符串，我如何将委托返回给该方法（该方法的？）？
Example:
例子：
MyDelegate GetByName(ISomeObject obj, string methodName)
{
...
return new MyDelegate(...);
}
ISomeObject someObject = ...;
MyDelegate myDelegate = GetByName(someObject, "ToString");
//myDelegate would be someObject.ToString
Thanks in advance.
提前致谢。
One more thing -- I really don't want to use a switch statement even though it would work but be a ton of code.
还有一件事——我真的不想使用 switch 语句，即使它可以工作但需要大量代码。
采纳答案by Jon Skeet
You'll need to use Type.GetMethodto get the right method, and Delegate.CreateDelegateto convert the MethodInfointo a delegate. Full example:
您需要使用Type.GetMethod来获取正确的方法，并将Delegate.CreateDelegate其转换MethodInfo为委托。完整示例：
using System;
using System.Reflection;
delegate string MyDelegate();
public class Dummy
{
public override string ToString()
{
return "Hi there";
}
}
public class Test
{
static MyDelegate GetByName(object target, string methodName)
{
MethodInfo method = target.GetType()
.GetMethod(methodName,
BindingFlags.Public
| BindingFlags.Instance
| BindingFlags.FlattenHierarchy);
// Insert appropriate check for method == null here
return (MyDelegate) Delegate.CreateDelegate
(typeof(MyDelegate), target, method);
}
static void Main()
{
Dummy dummy = new Dummy();
MyDelegate del = GetByName(dummy, "ToString");
Console.WriteLine(del());
}
}
Mehrdad's comment is a great one though - if the exceptions thrown by this overload of Delegate.CreateDelegateare okay, you can simplify GetByNamesignificantly:
不过，Mehrdad 的评论很棒——如果Delegate.CreateDelegate的这个重载抛出的异常没问题，你可以GetByName显着简化：
static MyDelegate GetByName(object target, string methodName)
{
return (MyDelegate) Delegate.CreateDelegate
(typeof(MyDelegate), target, methodName);
}
I've never used this myself, because I normally do other bits of checking after finding the MethodInfoexplicitly - but where it's suitable, this is really handy :)
我自己从来没有使用过这个，因为我通常会在MethodInfo明确找到后进行其他检查- 但在合适的地方，这真的很方便:)
回答by Mehrdad Afshari
static MyDelegate GetByName(object obj, string methodName)
{
return () => obj.GetType().InvokeMember(methodName,
System.Reflection.BindingFlags.InvokeMethod, null, obj, null);
}
回答by JoshBerke
Even easier is to use:
使用起来更简单：
public static MyDelegate GetByName(object target, string methodName)
{
return (MyDelegate)Delegate.CreateDelegate(typeof(MyDelegate),
target, methodName);
}
Notice that CreateDelegate has an overload which takes the methodName for you. This was done with .net 3.5 Sp1
请注意， CreateDelegate 有一个重载，它为您获取 methodName。这是用 .net 3.5 Sp1 完成的
