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[英]How to pass a delegate or function pointer from C# to C++ and call it there using InternalCall
[英]How to call delegate from string in C#?
是否可以通過變量名稱(作為字符串)調用存儲在變量中的委托? 我想我必須使用反射機制,但我沒有得到任何地方
示例代碼:
class Demo {
public delegate int DemoDelegate();
private static int One() {
return 1;
}
private static void CallDelegate(string name) {
// somehow get the value of the variable with the name
// stored in "name" and call the delegate using reflection
}
private static void CallDelegate(string name, DemoDelegate d) {
d();
}
static void main(string[] args) {
DemoDelegate one = Demo.One;
CallDelegate(one);
// this works, but i want to avoid writing the name of the variable/delegate twice:
CallDelegate("one", one);
}
}
這有可能嗎? 如果是這樣的話? 如果沒有,那么我必須使用第二種形式,運氣不好
變量幾乎不存在。 可靠地逐個字符串調用(在這種情況下)的唯一方法是將委托存儲在字典中:
Dictionary<string, DemoDelegate> calls = new Dictionary<string, DemoDelegate>
{
{"one",one}, {"two",two}
}
現在將字典存儲在某個地方(通常是在字段中 ),並執行以下操作:
private int CallDelegate(string name) {
return calls[name].Invoke(); // <==== args there if needed
}
是的,只要您使用Linq表達式,並且反射很少,就有可能。
看看這段代碼,它可以實現我想你想要的東西:
using System;
using System.Linq.Expressions;
using System.Reflection;
using System.Collections.Generic;
namespace q6010555
{
class Demo
{
static List<string> varNamesUsed = new List<string>();
public delegate int DemoDelegate();
private static int One()
{
return 1;
}
private static void CallDelegate(Expression<Func<DemoDelegate>> expr)
{
var lambda = expr as LambdaExpression;
var body = lambda.Body;
var field = body as MemberExpression;
var name = field.Member.Name;
var constant = field.Expression as ConstantExpression;
var value = (DemoDelegate)((field.Member as FieldInfo).GetValue(constant.Value));
// now you have the variable name... you may use it somehow!
// You could log the variable name.
varNamesUsed.Add(name);
value();
}
static void Main(string[] args)
{
DemoDelegate one = Demo.One;
CallDelegate(() => one);
// show used variable names
foreach (var item in varNamesUsed)
Console.WriteLine(item);
Console.ReadKey();
}
}
}
public void Fire(string name)
{
FieldInfo field = this.GetType().GetField(name, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
if (field != null)
{
Delegate method = field.GetValue(this) as Delegate;
if (method != null)
{
method.Method.Invoke(method.Target, new object[0]);
}
}
}
顯然會限制您使用參數化代理。
你無法真正訪問另一個堆棧框架中的變量(盡管我認為可以在StackFrame
類中使用hackery)。 相反,如果要以類似反射的方式調用通用委托,則需要傳遞Delegate
對象並使用DynamicInvoke
等方法。
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