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Accepted
Kalmankantaja
Asked:2023-02-24 21:31:00 +0800 CST2023-02-24 21:31:00 +0800 CST

如何从 CIL 访问字段

  • 772

有一类：

public class Test
{
   private string[] _array;

   public Test(int n)
   {
      _array = new string[n];
   }
   
   //return _array[i];
   public string Method(int i) 
   {
        var ownerType = this.GetType();
        DynamicMethod method = new DynamicMethod("test_method", 
                                                  typeof(string), 
                                                  new Type[] { typeof(int) },
                                                  ownerType );
        var generator = method.GetILGenerator();

        var arrayField = ownerType.GetField("_array", BindingFlags.NonPublic | BindingFlags.Instance);

        generator.Emit(OpCodes.Ldarg_0);
        generator.Emit(OpCodes.Ldfld, arrayField);
        generator.Emit(OpCodes.Ldarg_1);
        generator.Emit(OpCodes.Ldelem_Ref);
        generator.Emit(OpCodes.Ret);

        return (string)method.Invoke(null, new object[] { i });
   }
}

调用时Method会抛出异常 System.Reflection.TargetInvocationException: 'Exception has been thrown by the target of an invocation. Inner Exception: NullReferenceException: Object reference not set to an instance of an object.'。如何加载当前类实例以便其成员在 DynamicMethod 中可用？

c#

1 个回答

  1. Best Answer

    this作为第一个参数隐式传递。

    所以新方法实际上有2个参数

    new Type[] { ownerType, typeof(int) },

    而且，打电话的时候，你也必须同时通过

    method.Invoke(null, new object[] { this, i });
    • 1

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