FastPropertyAccessor.cs source code in C# .NET

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Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / Util / FastPropertyAccessor.cs / 3 / FastPropertyAccessor.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

using System; 
using System.Reflection; 
using System.Reflection.Emit;
using System.Threading; 
using System.Collections;
using System.Security;
using System.Security.Permissions;
 
namespace System.Web.Util {
    /* 
     * Property Accessor Generator class 
     *
     * The purpose of this class is to generate some IL code on the fly that can efficiently 
     * access properties (and fields) of objects.  This is an alternative to using
     * very slow reflection.
     */
 
    internal class FastPropertyAccessor {
 
        private static object s_lockObject = new object(); 
        private static FastPropertyAccessor s_accessorGenerator;
        private static Hashtable s_accessorCache; 
        private static MethodInfo _getPropertyMethod;
        private static MethodInfo _setPropertyMethod;
        private static Type[] _getPropertyParameterList = new Type[] { typeof(object) };
        private static Type[] _setPropertyParameterList = new Type[] { typeof(object), typeof(object) }; 
        private static Type[] _interfacesToImplement;
 
        private static int _uniqueId;   // Used to generate unique type ID's. 

        // Property getter/setter must be public for codegen to access it. 
        // Static properties are ignored, since this class only works on instances of objects.
        // Need to use DeclaredOnly to avoid AmbiguousMatchException if a property with
        // a different return type is hidden.
        private const BindingFlags _declaredFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly; 

        private ModuleBuilder _dynamicModule = null; 
 
        static FastPropertyAccessor() {
 
            // Get the SetProperty method, and make sure it has
            // the correct signature.

            _getPropertyMethod = typeof(IWebPropertyAccessor).GetMethod("GetProperty"); 
            _setPropertyMethod = typeof(IWebPropertyAccessor).GetMethod("SetProperty");
 
            // This will be needed later, when building the dynamic class. 
            _interfacesToImplement = new Type[1];
            _interfacesToImplement[0] = typeof(IWebPropertyAccessor); 
        }

        private static String GetUniqueCompilationName() {
            return Guid.NewGuid().ToString().Replace('-', '_'); 
        }
 
        [ReflectionPermission(SecurityAction.Assert, Flags=ReflectionPermissionFlag.ReflectionEmit)] 
        Type GetPropertyAccessorTypeWithAssert(Type type, string propertyName,
            PropertyInfo propInfo, FieldInfo fieldInfo) { 
            // Create the dynamic assembly if needed.
            Type accessorType;

            MethodInfo getterMethodInfo = null; 
            MethodInfo setterMethodInfo = null;
            Type propertyType; 
 
            if (propInfo != null) {
                // It'a a property 
                getterMethodInfo = propInfo.GetGetMethod();
                setterMethodInfo = propInfo.GetSetMethod();

                propertyType = propInfo.PropertyType; 
            }
            else { 
                // If not, it must be a field 
                propertyType = fieldInfo.FieldType;
            } 

            if (_dynamicModule == null) {
                lock (this) {
                    if (_dynamicModule == null) { 

                        // Use a unique name for each assembly. 
                        String name = GetUniqueCompilationName(); 

                        AssemblyName assemblyName = new AssemblyName(); 
                        assemblyName.Name = "A_" + name;

                        // Create a new assembly.
                        AssemblyBuilder newAssembly = 
                           Thread.GetDomain().DefineDynamicAssembly(assemblyName,
                                                                    AssemblyBuilderAccess.Run, 
                                                                    null, //directory to persist assembly 
                                                                    null, //evidence copied from caller
                                                                    null, //requiredPermissions 
                                                                    null, //optionalPermissions
                                                                    null, //refusedPermissions
                                                                    true //isSynchronized
                                                                    ); 

                        // Create a single module in the assembly. 
                        _dynamicModule = newAssembly.DefineDynamicModule("M_" + name); 
                    }
                } 
            }

            // Give the factory a unique name.
 
            String typeName = System.Web.UI.Util.MakeValidTypeNameFromString(type.Name) +
                "_" + propertyName + "_" + (_uniqueId++); 
 
            TypeBuilder accessorTypeBuilder = _dynamicModule.DefineType("T_" + typeName,
                                                                       TypeAttributes.Public, 
                                                                       typeof(object),
                                                                       _interfacesToImplement);

            // 
            // Define the GetProperty method. It must be virtual to be an interface implementation.
            // 
 
            MethodBuilder method = accessorTypeBuilder.DefineMethod("GetProperty",
                                                                   MethodAttributes.Public | 
                                                                        MethodAttributes.Virtual,
                                                                   typeof(Object),
                                                                   _getPropertyParameterList);
 
            // Generate IL. The generated IL corresponds to:
            //  "return ((TargetType) target).Blah;" 
 
            ILGenerator il = method.GetILGenerator();
            if (getterMethodInfo != null) { 
                il.Emit(OpCodes.Ldarg_1);
                il.Emit(OpCodes.Castclass, type);

                // Generate the getter call based on whether it's a Property or Field 
                if (propInfo != null)
                    il.EmitCall(OpCodes.Callvirt, getterMethodInfo, null); 
                else 
                    il.Emit(OpCodes.Ldfld, fieldInfo);
 
                il.Emit(OpCodes.Box, propertyType);
                il.Emit(OpCodes.Ret);

                // Specify that this method implements GetProperty from the inherited interface. 
                accessorTypeBuilder.DefineMethodOverride(method, _getPropertyMethod);
            } 
            else { 
                // Generate IL. The generated IL corresponds to "throw new InvalidOperationException"
                ConstructorInfo cons = typeof(InvalidOperationException).GetConstructor(Type.EmptyTypes); 
                il.Emit(OpCodes.Newobj, cons);
                il.Emit(OpCodes.Throw);
            }
 

            // 
            // Define the SetProperty method. It must be virtual to be an interface implementation. 
            //
 
            method = accessorTypeBuilder.DefineMethod("SetProperty",
                                                                   MethodAttributes.Public |
                                                                        MethodAttributes.Virtual,
                                                                   null, 
                                                                   _setPropertyParameterList);
 
            il = method.GetILGenerator(); 

            // Don't generate any code in the setter if it's a readonly property. 
            // We still need to have an implementation of SetProperty, but it does nothing.
            if (fieldInfo != null || setterMethodInfo != null) {

                // Generate IL. The generated IL corresponds to: 
                //  "((TargetType) target).Blah = (PropType) val;"
 
                il.Emit(OpCodes.Ldarg_1); 
                il.Emit(OpCodes.Castclass, type);
                il.Emit(OpCodes.Ldarg_2); 

                if (propertyType.IsPrimitive) {
                    // Primitive type: deal with boxing
                    il.Emit(OpCodes.Unbox, propertyType); 

                    // Emit the proper instruction for the type 
                    if (propertyType == typeof(sbyte)) { 
                        il.Emit(OpCodes.Ldind_I1);
                    } 
                    else if (propertyType == typeof(byte)) {
                        il.Emit(OpCodes.Ldind_U1);
                    }
                    else if (propertyType == typeof(short)) { 
                        il.Emit(OpCodes.Ldind_I2);
                    } 
                    else if (propertyType == typeof(ushort)) { 
                        il.Emit(OpCodes.Ldind_U2);
                    } 
                    else if (propertyType == typeof(uint)) {
                        il.Emit(OpCodes.Ldind_U4);
                    }
                    else if (propertyType == typeof(int)) { 
                        il.Emit(OpCodes.Ldind_I4);
                    } 
                    else if (propertyType == typeof(long)) { 
                        il.Emit(OpCodes.Ldind_I8);
                    } 
                    else if (propertyType == typeof(ulong)) {
                        il.Emit(OpCodes.Ldind_I8);  // Somehow, there is no Ldind_u8
                    }
                    else if (propertyType == typeof(bool)) { 
                        il.Emit(OpCodes.Ldind_I1);
                    } 
                    else if (propertyType == typeof(char)) { 
                        il.Emit(OpCodes.Ldind_U2);
                    } 
                    else if (propertyType == typeof(decimal)) {
                        il.Emit(OpCodes.Ldobj, propertyType);
                    }
                    else if (propertyType == typeof(float)) { 
                        il.Emit(OpCodes.Ldind_R4);
                    } 
                    else if (propertyType == typeof(double)) { 
                        il.Emit(OpCodes.Ldind_R8);
                    } 
                    else {
                        il.Emit(OpCodes.Ldobj, propertyType);
                    }
                } 
                else if (propertyType.IsValueType) {
                    // Value type: deal with boxing 
                    il.Emit(OpCodes.Unbox, propertyType); 
                    il.Emit(OpCodes.Ldobj, propertyType);
                } 
                else {
                    // No boxing involved: just generate a standard cast
                    il.Emit(OpCodes.Castclass, propertyType);
                } 

                // Generate the assignment based on whether it's a Property or Field 
                if (propInfo != null) 
                    il.EmitCall(OpCodes.Callvirt, setterMethodInfo, null);
                else 
                    il.Emit(OpCodes.Stfld, fieldInfo);
            }

            il.Emit(OpCodes.Ret); 

            // Specify that this method implements SetProperty from the inherited interface. 
            accessorTypeBuilder.DefineMethodOverride(method, _setPropertyMethod); 

            // Bake in the type. 
            accessorType = accessorTypeBuilder.CreateType();

            return accessorType;
        } 

        private static IWebPropertyAccessor GetPropertyAccessor(Type type, string propertyName) { 
 
            if (s_accessorGenerator == null || s_accessorCache == null) {
                lock (s_lockObject) { 
                    if (s_accessorGenerator == null || s_accessorCache == null) {
                        s_accessorGenerator = new FastPropertyAccessor();
                        s_accessorCache = new Hashtable();
                    } 
                }
            } 
 
            // First, check if we have it cached
 
            // Get a hash key based on the Type and the property name
            int cacheKey = HashCodeCombiner.CombineHashCodes(
                type.GetHashCode(), propertyName.GetHashCode());
 
            IWebPropertyAccessor accessor = (IWebPropertyAccessor) s_accessorCache[cacheKey];
 
            // It was cached, so just return it 
            if (accessor != null)
                return accessor; 

            FieldInfo fieldInfo = null;
            Type declaringType;
 
            // First, try to find a property with that name.  Type.GetProperty() without BindingFlags.Declared
            // will throw AmbiguousMatchException if there is a hidden property with the same name and a 
            // different type (VSWhidbey 237437).  This method finds the property with the specified name 
            // on the most specific type.
            PropertyInfo propInfo = GetPropertyMostSpecific(type, propertyName); 

            if (propInfo != null) {
                // Get the most base Type where the property is first declared
                MethodInfo baseCheckMethodInfo = propInfo.GetGetMethod(); 
                if (baseCheckMethodInfo == null) {
                    baseCheckMethodInfo = propInfo.GetSetMethod(); 
                } 
                declaringType = baseCheckMethodInfo.GetBaseDefinition().DeclaringType;
 
                // DevDiv Bug 27734
                // Ignore the declaring type if it's generic
                if (declaringType.IsGenericType)
                    declaringType = type; 

                // If they're different, get a new PropertyInfo 
                if (declaringType != type) { 
                    // We want the propertyInfo for the property specifically declared on the declaringType.
                    // So pass in the correct BindingFlags to avoid an AmbiguousMatchException, which would 
                    // be thrown if the declaringType hides a property with the same name and a different type.
                    // VSWhidbey 518034
                    propInfo = declaringType.GetProperty(propertyName, _declaredFlags);
                } 
            }
            else { 
                // We couldn't find a property, so try a field 
                // Type.GetField can not throw AmbiguousMatchException like Type.GetProperty above.
                fieldInfo = type.GetField(propertyName); 

                // If we couldn't find a field either, give up
                if (fieldInfo == null)
                    throw new ArgumentException(); 

                declaringType = fieldInfo.DeclaringType; 
            } 

            // If the Type where the property/field is declared is not the same as the current 
            // Type, check if the declaring Type already has a cached accessor.  This limits
            // the number of different accessors we need to create.  e.g. Every control has
            // an ID property, but we'll end up only create one accessor for all of them.
            int declaringTypeCacheKey = 0; 
            if (declaringType != type) {
                // Get a hash key based on the declaring Type and the property name 
                declaringTypeCacheKey = HashCodeCombiner.CombineHashCodes( 
                    declaringType.GetHashCode(), propertyName.GetHashCode());
 
                accessor = (IWebPropertyAccessor) s_accessorCache[declaringTypeCacheKey];

                // We have a cached accessor for the declaring type, so use it
                if (accessor != null) { 

                    // Cache the declaring type's accessor as ourselves 
                    lock (s_accessorCache.SyncRoot) { 
                        s_accessorCache[cacheKey] = accessor;
                    } 

                    return accessor;
                }
            } 

            if (accessor == null) { 
                Type propertyAccessorType; 

                lock (s_accessorGenerator) { 
                    propertyAccessorType = s_accessorGenerator.GetPropertyAccessorTypeWithAssert(
                        declaringType, propertyName, propInfo, fieldInfo);
                }
 
                // Create the type. This is the only place where Activator.CreateInstance is used,
                // reducing the calls to it from 1 per instance to 1 per type. 
                accessor = (IWebPropertyAccessor) HttpRuntime.CreateNonPublicInstance(propertyAccessorType); 
            }
 
            // Cache the accessor
            lock (s_accessorCache.SyncRoot) {
                s_accessorCache[cacheKey] = accessor;
 
                if (declaringTypeCacheKey != 0)
                    s_accessorCache[declaringTypeCacheKey] = accessor; 
            } 

            return accessor; 
        }

        internal static object GetProperty(object target, string propName) {
            IWebPropertyAccessor accessor = GetPropertyAccessor(target.GetType(), propName); 
            return accessor.GetProperty(target);
        } 
 
        // Finds the property with the specified name on the most specific type.
        private static PropertyInfo GetPropertyMostSpecific(Type type, string name) { 
            PropertyInfo propInfo;
            Type currentType = type;

            while (currentType != null) { 
                propInfo = currentType.GetProperty(name, _declaredFlags);
                if (propInfo != null) { 
                    return propInfo; 
                }
                else { 
                    currentType = currentType.BaseType;
                }
            }
 
            return null;
        } 
 
        internal static void SetProperty(object target, string propName, object val) {
            IWebPropertyAccessor accessor = GetPropertyAccessor(target.GetType(), propName); 
            accessor.SetProperty(target, val);
        }
    }
 
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    public interface IWebPropertyAccessor { 
        object GetProperty(object target);
        void SetProperty(object target, object value); 
    }
}

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