using System;
using System.Reflection;
using System.Reflection.Emit;

public class DynamicFieldGetter
{
    public static Func<object, object> CreateFieldGetter(FieldInfo fieldInfo)
    {
        // 创建动态方法
        DynamicMethod dynamicMethod = new DynamicMethod(
            name: $"Get_{fieldInfo.Name}",
            returnType: typeof(object),
            parameterTypes: new[] { typeof(object) },
            restrictedSkipVisibility: true);

        // 获取IL生成器
        ILGenerator il = dynamicMethod.GetILGenerator();

        // 加载参数(对象实例)
        il.Emit(OpCodes.Ldarg_0);

        // 如果是静态字段，不需要加载实例
        if (!fieldInfo.IsStatic)
        {
            // 如果字段是值类型，需要拆箱
            if (fieldInfo.DeclaringType.IsValueType)
            {
                il.Emit(OpCodes.Unbox, fieldInfo.DeclaringType);
            }
            else
            {
                il.Emit(OpCodes.Castclass, fieldInfo.DeclaringType);
            }
        }

        // 获取字段值
        il.Emit(fieldInfo.IsStatic ? OpCodes.Ldsfld : OpCodes.Ldfld, fieldInfo);

        // 如果字段是值类型，需要装箱
        if (fieldInfo.FieldType.IsValueType)
        {
            il.Emit(OpCodes.Box, fieldInfo.FieldType);
        }

        // 返回结果
        il.Emit(OpCodes.Ret);

        // 创建并返回委托
        return (Func<object, object>)dynamicMethod.CreateDelegate(typeof(Func<object, object>));
    }
}

public class TestClass
{
    public string Name = "Test";
    public int Age = 25;
    public static double PI = 3.14159;
}

class Program
{
    static void Main()
    {
        // 获取字段信息
        FieldInfo nameField = typeof(TestClass).GetField("Name");
        FieldInfo ageField = typeof(TestClass).GetField("Age");
        FieldInfo piField = typeof(TestClass).GetField("PI");

        // 创建动态getter
        var getName = DynamicFieldGetter.CreateFieldGetter(nameField);
        var getAge = DynamicFieldGetter.CreateFieldGetter(ageField);
        var getPi = DynamicFieldGetter.CreateFieldGetter(piField);

        // 创建测试实例
        var testObj = new TestClass();

        // 使用动态getter
        Console.WriteLine(getName(testObj));  // 输出: Test
        Console.WriteLine(getAge(testObj));   // 输出: 25
        Console.WriteLine(getPi(null));      // 输出: 3.14159 (静态字段)
    }
}

new DynamicMethod(..., restrictedSkipVisibility: true);

if (fieldInfo.DeclaringType.IsValueType)
{
    il.Emit(OpCodes.Unbox, fieldInfo.DeclaringType);
}
if (fieldInfo.FieldType.IsValueType)
{
    il.Emit(OpCodes.Box, fieldInfo.FieldType);
}

il.Emit(fieldInfo.IsStatic ? OpCodes.Ldsfld : OpCodes.Ldfld, fieldInfo);