Reflection and boxing value types
我正在编写一个类,该类可以通过反射使用字符串模式从对象获取和设置值。该类即使在复杂的模式下也能很好地运行,但是出现了我不知道如何解决/解决问题的意外行为。
本质上,当类访问值类型的字段或属性时,一切正常,但对值类型的副本进行操作。确实,当我使用字符串模式设置值时,实际值类型不会被更新。
该类包含一个
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | private static object GetObjectMemberValue(object obj, MemberInfo memberInfo, object[] memberArgs) { if (memberInfo == null) throw new ArgumentNullException("memberInfo"); // Get the value switch (memberInfo.MemberType) { case MemberTypes.Field: { FieldInfo fieldInfo = (FieldInfo)memberInfo; if (fieldInfo.FieldType.IsValueType) { TypedReference typedReference = __makeref(obj); return (fieldInfo.GetValueDirect(typedReference)); } else return (fieldInfo.GetValue(obj)); } case MemberTypes.Property: return (((PropertyInfo)memberInfo).GetValue(obj, memberArgs)); case MemberTypes.Method: return (((MethodInfo)memberInfo).Invoke(obj, memberArgs)); default: throw new InvalidOperationException(String.Format("the type of the member {0}.{1} is not supported", obj.GetType().Name, memberInfo.Name)); } } private static void SetObjectMemberValue(object obj, MemberInfo memberInfo, params object[] memberArgs) { if (memberInfo == null) throw new ArgumentNullException("memberInfo"); // Set the value switch (memberInfo.MemberType) { case MemberTypes.Field: { FieldInfo fieldInfo = (FieldInfo)memberInfo; if (fieldInfo.FieldType.IsValueType) { TypedReference typedReference = __makeref(obj); fieldInfo.SetValueDirect(typedReference, memberArgs[0]); } else fieldInfo.SetValue(obj, memberArgs[0]); } break; case MemberTypes.Property: ((PropertyInfo)memberInfo).SetValue(obj, memberArgs[0], null); break; case MemberTypes.Method: ((MethodInfo)memberInfo).Invoke(obj, memberArgs); break; default: throw new InvalidOperationException(String.Format("the type of the member {0}.{1} is not supported", obj.GetType().Name, memberInfo.Name)); } } |
当
我该如何解决?我已经检查了这个问题,但是没有成功(您可以在字段管理中看到代码):由于将字段值分配给对象变量,所以装箱操作完全相同。
使情况更清楚,这是所讨论类的完整代码:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 | // Copyright (C) 2012 Luca Piccioni // // This program is free software: you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program. If not, see <http://www.gnu.org/licenses/>. using System; using System.Collections.Generic; using System.Diagnostics; using System.Reflection; using System.Text; using System.Text.RegularExpressions; namespace Derm { /// <summary> /// Class able to read and write a generic object. /// </summary> /// <remarks> /// <para> /// This class supports the access to one of the following: /// - A specific object field /// - A specific object property (even indexed) /// - A specific object method (even with arguments) /// </para> /// </remarks> public class ObjectAccessor { #region Constructors /// <summary> /// Construct an ObjectAccessor that access to an object's field or property. /// </summary> /// <param name="container"> /// A <see cref="System.Object"/> that specify a generic member. /// </param> /// <param name="memberPattern"> /// A <see cref="System.String"/> that specify the pattern of the member of <paramref name="container"/>. /// </param> public ObjectAccessor(object container, string memberPattern) { if (container == null) throw new ArgumentNullException("container"); if (memberPattern == null) throw new ArgumentNullException("memberPattern"); // Store member pattern mMemberPattern = memberPattern; Dictionary<int, string> stringMap = new Dictionary<int,string>(); object containerMember = container; int stringMapIndex = 0; // Remove (temporarly) strings enclosed by double-quotes memberPattern = Regex.Replace(memberPattern,""[^\\\"]*"", delegate(Match match) { stringMap[stringMapIndex++] = match.Value; return (String.Format("{{{0}}}", stringMapIndex - 1)); }); string[] members = Regex.Split(memberPattern, @"\\."); // Restore strings enclosed by double-quotes for (int i = 0; i < members.Length; i++ ) { members[i] = Regex.Replace(members[i], @"{(?<StringOrder>\\d+)}", delegate(Match match) { return (stringMap[Int32.Parse(match.Groups["StringOrder"].Value)]); }); } if (members.Length > 1) { StringBuilder containerMemberPattern = new StringBuilder(memberPattern.Length); for (int i = 0; i < members.Length - 1; i++ ) { MemberInfo memberInfo; object[] memberArgs; // Pattern for exception message containerMemberPattern.AppendFormat(".{0}", members[i]); // Access to the (intermediate) member GetObjectMember(containerMember, members[i], out memberInfo, out memberArgs); // Get member value containerMember = GetObjectMemberValue(containerMember, memberInfo, memberArgs); if (containerMember == null) throw new InvalidOperationException(String.Format("the field {0} is null", containerMemberPattern.ToString())); if ((memberInfo.MemberType != MemberTypes.Field) && (containerMember.GetType().IsValueType == true)) throw new NotSupportedException("invalid pattern becuase operating on strcuture copy"); } } // Store container object mContainer = container; // Store object mObject = containerMember; // Get member GetObjectMember(mObject, members[members.Length - 1], out mMember, out mMemberArgs); } #endregion #region Object Access /// <summary> /// Get the type of the accessed member. /// </summary> public Type MemberType { get { switch (mMember.MemberType) { case MemberTypes.Field: return (((FieldInfo)mMember).FieldType); case MemberTypes.Property: return (((PropertyInfo)mMember).PropertyType); default: throw new NotSupportedException(mMember.MemberType +" is not supported"); } } } /// <summary> /// Get the value of the object member. /// </summary> /// <returns></returns> public object Get() { switch (mMember.MemberType) { case MemberTypes.Field: { FieldInfo fieldInfo = (FieldInfo)mMember; if (fieldInfo.FieldType.IsValueType) { object referenceObject = mObject; TypedReference typedReference = __makeref(referenceObject); return (fieldInfo.GetValueDirect(typedReference)); } else return (fieldInfo.GetValue(mObject)); } case MemberTypes.Property: if (((PropertyInfo)mMember).CanRead == false) throw new InvalidOperationException("write-only property"); return (((PropertyInfo)mMember).GetValue(mObject, null)); default: throw new NotSupportedException(mMember.MemberType +" is not supported"); } } /// <summary> /// Set the value of the object member. /// </summary> /// <param name="value"></param> public void Set(object value) { switch (mMember.MemberType) { case MemberTypes.Field: { FieldInfo fieldInfo = (FieldInfo)mMember; if (fieldInfo.FieldType.IsValueType) { object referenceObject = mObject; TypedReference typedReference = __makeref(referenceObject); fieldInfo.SetValueDirect(typedReference, value); } else fieldInfo.SetValue(mObject, value); } break; case MemberTypes.Property: if (((PropertyInfo)mMember).CanWrite == false) throw new InvalidOperationException("read-only property"); ((PropertyInfo)mMember).SetValue(mObject, value, null); break; default: throw new NotSupportedException(mMember.MemberType +" is not supported"); } } /// <summary> /// The object used for getting the object implementing <see cref="mMember"/>. In simple cases /// it equals <see cref="mObject"/>. /// </summary> private readonly object mContainer; /// <summary> /// The object that specify the field/property pointed by <see cref="mMember"/>. /// </summary> private readonly object mObject; /// <summary> /// The pattern used for getting/setting the member of <see cref="mObject"/>. /// </summary> private readonly string mMemberPattern; /// <summary> /// Field, property or method member of <see cref="mObject"/>. /// </summary> private readonly MemberInfo mMember; /// <summary> /// Arguments list specified at member invocation. /// </summary> private readonly object[] mMemberArgs; #endregion #region Object Member Access /// <summary> /// Access to an object member. /// </summary> /// <param name="obj"> /// A <see cref="System.Object"/> which type defines the underlying member. /// </param> /// <param name="memberPattern"> /// A <see cref="System.String"/> that specify how the member is identified. For methods and indexed properties, the arguments /// list is specified also. /// </param> /// <param name="memberInfo"> /// A <see cref="System.Reflection.MemberInfo"/> that represent the member. /// </param> /// <param name="memberArgs"> /// An array of <see cref="System.Object"/> that represent the argument list required for calling a method or an indexed /// property. /// </param> private static void GetObjectMember(object obj, string memberPattern, out MemberInfo memberInfo, out object[] memberArgs) { if (obj == null) throw new ArgumentNullException("obj"); if (memberPattern == null) throw new ArgumentNullException("memberPattern"); Type objType = obj.GetType(); Match methodMatch; if ((methodMatch = sCollectionRegex.Match(memberPattern)).Success || (methodMatch = sMethodRegex.Match(memberPattern)).Success) { MemberInfo[] members = objType.GetMember(methodMatch.Groups["MethodName"].Value); ParameterInfo[] methodArgsInfo; int bestMemberIndex = 0; if ((members == null) || (members.Length == 0)) throw new InvalidOperationException(String.Format("no property/method {0}", memberPattern)); string[] args = Regex.Split(methodMatch.Groups["MethodArgs"].Value," *, *"); if (members.Length != 1) { Type[] argsType = new Type[args.Length]; bestMemberIndex = -1; // Try to guess method arguments type to identify the best overloaded match for (int i = 0; i < args.Length; i++) argsType[i] = GuessMethodArgumentType(args[i]); if (Array.TrueForAll<Type>(argsType, delegate(Type type) { return (type != null); })) { for (int i = 0; i < members.Length; i++) { if (members[i].MemberType == MemberTypes.Property) { methodArgsInfo = ((PropertyInfo)members[i]).GetIndexParameters(); Debug.Assert((methodArgsInfo != null) && (methodArgsInfo.Length > 0)); } else if (members[i].MemberType == MemberTypes.Method) { methodArgsInfo = ((MethodInfo)members[i]).GetParameters(); } else throw new NotSupportedException("neither a method or property"); // Parameters count mismatch? if (methodArgsInfo.Length != args.Length) continue; // Parameter type incompatibility? bool compatibleArgs = true; for (int j = 0; j < args.Length; j++) { if (argsType[j] != methodArgsInfo[j].ParameterType) { compatibleArgs = false; break; } } if (compatibleArgs == false) continue; bestMemberIndex = i; break; } } if (bestMemberIndex == -1) throw new InvalidOperationException(String.Format("method or property {0} has an ambiguous definition", memberPattern)); } // Method or indexed property memberInfo = members[bestMemberIndex]; // Parse method arguments if (memberInfo.MemberType == MemberTypes.Property) { methodArgsInfo = ((PropertyInfo)memberInfo).GetIndexParameters(); Debug.Assert((methodArgsInfo != null) && (methodArgsInfo.Length > 0)); } else if (memberInfo.MemberType == MemberTypes.Method) { methodArgsInfo = ((MethodInfo)memberInfo).GetParameters(); } else throw new NotSupportedException("neither a method or property"); if (args.Length != methodArgsInfo.Length) throw new InvalidOperationException("argument count mismatch"); memberArgs = new object[args.Length]; for (int i = 0; i < args.Length; i++) { Type argType = methodArgsInfo[i].ParameterType; if (argType == typeof(String)) { memberArgs[i] = args[i].Substring(1, args[i].Length - 2); } else if (argType == typeof(Int32)) { memberArgs[i] = Int32.Parse(args[i]); } else if (argType == typeof(UInt32)) { memberArgs[i] = UInt32.Parse(args[i]); } else if (argType == typeof(Single)) { memberArgs[i] = Single.Parse(args[i]); } else if (argType == typeof(Double)) { memberArgs[i] = Double.Parse(args[i]); } else if (argType == typeof(Int16)) { memberArgs[i] = Int16.Parse(args[i]); } else if (argType == typeof(UInt16)) { memberArgs[i] = UInt16.Parse(args[i]); } else if (argType == typeof(Char)) { memberArgs[i] = Char.Parse(args[i]); } else if (argType == typeof(Byte)) { memberArgs[i] = Byte.Parse(args[i]); } else throw new InvalidOperationException(String.Format("argument of type {0} is not supported", argType.Name)); } } else { MemberInfo[] members = objType.GetMember(memberPattern); if ((members == null) || (members.Length == 0)) throw new InvalidOperationException(String.Format("no property/field {0}", memberPattern)); if (members.Length > 1) { members = Array.FindAll<MemberInfo>(members, delegate(MemberInfo member) { return (member.MemberType == MemberTypes.Property || member.MemberType == MemberTypes.Field); }); } if (members.Length != 1) throw new InvalidOperationException(String.Format("field of property {0} has an ambiguous definition", memberPattern)); // Property of field memberInfo = members[0]; // Not an indexed property memberArgs = null; } } /// <summary> /// Access to the object member. /// </summary> /// <param name="obj"> /// A <see cref="System.Object"/> which type defines the underlying member. /// </param> /// <param name="memberInfo"> /// A <see cref="System.Reflection.MemberInfo"/> that represent the member. /// </param> /// <param name="memberArgs"> /// An array of <see cref="System.Object"/> that represent the argument list required for calling a method or an indexed /// property. /// </param> /// <returns></returns> private static object GetObjectMemberValue(object obj, MemberInfo memberInfo, object[] memberArgs) { if (memberInfo == null) throw new ArgumentNullException("memberInfo"); // Get the value switch (memberInfo.MemberType) { case MemberTypes.Field: { FieldInfo fieldInfo = (FieldInfo)memberInfo; if (fieldInfo.FieldType.IsValueType) { TypedReference typedReference = __makeref(obj); return (fieldInfo.GetValueDirect(typedReference)); } else return (fieldInfo.GetValue(obj)); } case MemberTypes.Property: return (((PropertyInfo)memberInfo).GetValue(obj, memberArgs)); case MemberTypes.Method: return (((MethodInfo)memberInfo).Invoke(obj, memberArgs)); default: throw new InvalidOperationException(String.Format("the type of the member {0}.{1} is not supported", obj.GetType().Name, memberInfo.Name)); } } private static void SetObjectMemberValue(object obj, MemberInfo memberInfo, params object[] memberArgs) { if (memberInfo == null) throw new ArgumentNullException("memberInfo"); // Set the value switch (memberInfo.MemberType) { case MemberTypes.Field: { FieldInfo fieldInfo = (FieldInfo)memberInfo; if (fieldInfo.FieldType.IsValueType) { TypedReference typedReference = __makeref(obj); fieldInfo.SetValueDirect(typedReference, memberArgs[0]); } else fieldInfo.SetValue(obj, memberArgs[0]); } break; case MemberTypes.Property: ((PropertyInfo)memberInfo).SetValue(obj, memberArgs[0], null); break; case MemberTypes.Method: ((MethodInfo)memberInfo).Invoke(obj, memberArgs); break; default: throw new InvalidOperationException(String.Format("the type of the member {0}.{1} is not supported", obj.GetType().Name, memberInfo.Name)); } } private static Type GuessMethodArgumentType(string methodArg) { if (String.IsNullOrEmpty(methodArg)) throw new ArgumentNullException("methodArg"); if (sMethodArgString.IsMatch(methodArg)) return (typeof(String)); return (null); } /// <summary> /// Regular expression used for matching method calls. /// </summary> private static readonly Regex sMethodRegex = new Regex(@"^(?<MethodName>\\w+) *\\( *(?<MethodArgs>.*) *\\)$"); /// <summary> /// Regular expression used for matching method string arguments. /// </summary> private static readonly Regex sMethodArgString = new Regex(@""".*"""); /// <summary> /// Regular expression used for matching collection indexer calls. /// </summary> private static readonly Regex sCollectionRegex = new Regex(@"^(?<MethodName>\\w+) *\\[ *(?<MethodArgs>.*) *\\]$"); #endregion } } |
__ makeref是未记录的关键字。我从未见过使用过它,所以不确切知道它在做什么。但是,您可以通过在修改之前将值类型强制转换为对象来实现__makeref尝试执行的操作。
Jon Skeet解释了此答案的具体内容
https://stackoverflow.com/a/6280540/141172
顺便提一句,未记录的事物可以随着时间变化。我不会依靠它们来生产代码。
如果将
我不确定为什么字段类型是否为值类型与之相关。我以为我们在讨论
添加项:
我已经考虑了一下,如果您有拳击,我不再认为它可以使参数
我认为您的问题仅在于Set方法?您似乎没有使用
1 2 3 | var myMutableStruct = XXX; SetObjectMemberValue(myMutableStruct, instanceFieldInfo, 42); // use myMutableStruct with new field value |
这永远不能与结构一起使用,因为它是传递给方法的盒装副本。无论该方法做什么,它都只能访问该副本。相反,您可以说:
1 2 3 4 5 | var myMutableStruct = XXX; object boxToKeep = myMutableStruct; SetObjectMemberValue(myMutableStruct, instanceFieldInfo, 42); myMutableStruct = (MyMutableStruct)boxToKeep; // use myMutableStruct with new field value |
如果您不喜欢此方法,请尝试使该方法的通用类型为