70 lines
3.2 KiB
C#
70 lines
3.2 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="ReflectionUtil.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//------------------------------------------------------------------------------
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namespace System.Web.Util {
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using System;
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using System.Reflection;
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using System.Reflection.Emit;
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using System.Security.Permissions;
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// Provides helper methods for performing reflection over managed objects.
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[SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode = true)]
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internal static class ReflectionUtil {
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// Resets an object to its "default" state, e.g. where each instance field is given the value default(TField).
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public static void Reset<T>(T obj) where T : class {
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ResetUtil<T>.ResetFn(obj);
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}
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private static class ResetUtil<T> where T : class {
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internal readonly static Action<T> ResetFn = CreateResetFn();
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private static Action<T> CreateResetFn() {
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Type targetType = typeof(T);
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DynamicMethod dynamicMethod = CreateDynamicMethodWithAssert();
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ILGenerator ilGen = dynamicMethod.GetILGenerator();
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// for each field in the target type, reset to default(TField)
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FieldInfo[] allFields = targetType.GetFields(BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.NonPublic | BindingFlags.Public);
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foreach (FieldInfo fieldInfo in allFields) {
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if (fieldInfo.IsInitOnly || fieldInfo.IsDefined(typeof(DoNotResetAttribute))) {
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// This field is not eligible to be reset because it is marked readonly or [DoNotReset].
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continue;
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}
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// obj.field = default(TField);
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// Opcodes.Initobj can be used for both value and reference types; see ECMA 335, Partition III, Sec. 4.5 "initobj"
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// (ref: http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-335.pdf)
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ilGen.Emit(OpCodes.Ldarg_0);
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ilGen.Emit(OpCodes.Ldflda, fieldInfo);
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ilGen.Emit(OpCodes.Initobj, fieldInfo.FieldType);
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}
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ilGen.Emit(OpCodes.Ret);
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// dynamicMethod = obj => {
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// obj.field1 = default(TField1);
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// obj.field2 = default(TField2);
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// ...
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// };
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return (Action<T>)dynamicMethod.CreateDelegate(typeof(Action<T>));
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}
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[ReflectionPermission(SecurityAction.Assert, MemberAccess = true)] // needed to create a DynamicMethod inside the target type
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private static DynamicMethod CreateDynamicMethodWithAssert() {
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Type targetType = typeof(T);
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return new DynamicMethod(
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name: "Reset-" + targetType.Name,
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returnType: typeof(void),
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parameterTypes: new Type[] { targetType },
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owner: targetType,
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skipVisibility: true);
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}
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}
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}
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}
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