如何获取方法(.NET)中使用的字段？

Question

在.NET中,使用反射如何获取方法中使用的类变量？

例如:

class A
{
    UltraClass B = new(..);
    SupaClass C = new(..);

    void M1()
    {
        B.xyz(); // it can be a method call
        int a = C.a; // a variable access
    }
}

注意:GetClassVariablesInMethod(M1 MethodInfo)返回B和C变量.通过变量,我指的是该特定变量的Value和/或Type和Constructor Parameters.

Answer 1

有很多不同的答案,但由于没有一个人吸引我,这是我的.它使用我的基于反射的IL读取器.

这是一个检索方法使用的所有字段的方法:

static IEnumerable<FieldInfo> GetUsedFields (MethodInfo method)
{
    return (from instruction in method.GetInstructions ()
           where instruction.OpCode.OperandType == OperandType.InlineField
           select (FieldInfo) instruction.Operand).Distinct ();
}

Answer 2

这是正确答案的完整版本。这使用了其他答案中的材料，但包含了一个其他人没有发现的重要错误修复。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;

namespace Timwi.ILReaderExample
{
    public class ILReader
    {
        public class Instruction
        {
            public int StartOffset { get; private set; }
            public OpCode OpCode { get; private set; }
            public long? Argument { get; private set; }
            public Instruction(int startOffset, OpCode opCode, long? argument)
            {
                StartOffset = startOffset;
                OpCode = opCode;
                Argument = argument;
            }
            public override string ToString()
            {
                return OpCode.ToString() + (Argument == null ? string.Empty : " " + Argument.Value);
            }
        }

        private Dictionary<short, OpCode> _opCodeList;

        public ILReader()
        {
            _opCodeList = typeof(OpCodes).GetFields().Where(f => f.FieldType == typeof(OpCode)).Select(f => (OpCode) f.GetValue(null)).ToDictionary(o => o.Value);
        }

        public IEnumerable<Instruction> ReadIL(MethodBase method)
        {
            MethodBody body = method.GetMethodBody();
            if (body == null)
                yield break;

            int offset = 0;
            byte[] il = body.GetILAsByteArray();
            while (offset < il.Length)
            {
                int startOffset = offset;
                byte opCodeByte = il[offset];
                short opCodeValue = opCodeByte;
                offset++;

                // If it's an extended opcode then grab the second byte. The 0xFE prefix codes aren't marked as prefix operators though.
                if (opCodeValue == 0xFE || _opCodeList[opCodeValue].OpCodeType == OpCodeType.Prefix)
                {
                    opCodeValue = (short) ((opCodeValue << 8) + il[offset]);
                    offset++;
                }

                OpCode code = _opCodeList[opCodeValue];

                Int64? argument = null;

                int argumentSize = 4;
                if (code.OperandType == OperandType.InlineNone)
                    argumentSize = 0;
                else if (code.OperandType == OperandType.ShortInlineBrTarget || code.OperandType == OperandType.ShortInlineI || code.OperandType == OperandType.ShortInlineVar)
                    argumentSize = 1;
                else if (code.OperandType == OperandType.InlineVar)
                    argumentSize = 2;
                else if (code.OperandType == OperandType.InlineI8 || code.OperandType == OperandType.InlineR)
                    argumentSize = 8;
                else if (code.OperandType == OperandType.InlineSwitch)
                {
                    long num = il[offset] + (il[offset + 1] << 8) + (il[offset + 2] << 16) + (il[offset + 3] << 24);
                    argumentSize = (int) (4 * num + 4);
                }

                // This does not currently handle the 'switch' instruction meaningfully.
                if (argumentSize > 0)
                {
                    Int64 arg = 0;
                    for (int i = 0; i < argumentSize; ++i)
                    {
                        Int64 v = il[offset + i];
                        arg += v << (i * 8);
                    }
                    argument = arg;
                    offset += argumentSize;
                }

                yield return new Instruction(startOffset, code, argument);
            }
        }
    }

    public static partial class Program
    {
        public static void Main(string[] args)
        {
            var reader = new ILReader();
            var module = typeof(Program).Module;
            foreach (var instruction in reader.ReadIL(typeof(Program).GetMethod("Main")))
            {
                string arg = instruction.Argument.ToString();
                if (instruction.OpCode == OpCodes.Ldfld || instruction.OpCode == OpCodes.Ldflda || instruction.OpCode == OpCodes.Ldsfld || instruction.OpCode == OpCodes.Ldsflda || instruction.OpCode == OpCodes.Stfld)
                    arg = module.ResolveField((int) instruction.Argument).Name;
                else if (instruction.OpCode == OpCodes.Call || instruction.OpCode == OpCodes.Calli || instruction.OpCode == OpCodes.Callvirt)
                    arg = module.ResolveMethod((int) instruction.Argument).Name;
                else if (instruction.OpCode == OpCodes.Newobj)
                    // This displays the type whose constructor is being called, but you can also determine the specific constructor and find out about its parameter types
                    arg = module.ResolveMethod((int) instruction.Argument).DeclaringType.FullName;
                else if (instruction.OpCode == OpCodes.Ldtoken)
                    arg = module.ResolveMember((int) instruction.Argument).Name;
                else if (instruction.OpCode == OpCodes.Ldstr)
                    arg = module.ResolveString((int) instruction.Argument);
                else if (instruction.OpCode == OpCodes.Constrained || instruction.OpCode == OpCodes.Box)
                    arg = module.ResolveType((int) instruction.Argument).FullName;
                else if (instruction.OpCode == OpCodes.Switch)
                    // For the 'switch' instruction, the "instruction.Argument" is meaningless. You'll need extra code to handle this.
                    arg = "?";
                Console.WriteLine(instruction.OpCode + " " + arg);
            }
            Console.ReadLine();
        }
    }
}