custom object - Page 112

in java what is a Scanner object?

Dynamic object property populator (without reflection)

I want to populate an object's properties without using reflection in a manner similar to the DynamicBuilder on CodeProject. The CodeProject example is tailored for populating entities using a DataReader or DataRecord. I use this in several DALs to good effect. Now I want to modify it to use a dictionary or other data agnostic object so that I can use it in non DAL code --places I currently use reflection. I know almost nothing about OpCodes and IL. I just know that it works well and is faster than reflection. I have tried to modify the CodeProject example and because of my ignorance with IL, I have gotten stuck on two lines. One of them deals with dbnulls and I'm pretty sure I can just lose it, but I don't know if the lines preceding and following it are related and which of them will also need to go. The other, I think, is the one that pulled the value out of the datarecord before and now needs to pull it out of the dictionary. I think I can replace the "getValueMethod" with my "property.Value" but I'm not sure. I'm open to alternative/better ways of skinning this cat too. Here's the code so far (the commented out lines are the ones I'm stuck on): using System; using System.Collections.Generic; using System.Reflection; using System.Reflection.Emit; public class Populator<T> { private delegate T Load(Dictionary<string, object> properties); private Load _handler; private Populator() { } public T Build(Dictionary<string, object> properties) { return _handler(properties); } public static Populator<T> CreateBuilder(Dictionary<string, object> properties) { //private static readonly MethodInfo getValueMethod = typeof(IDataRecord).GetMethod("get_Item", new [] { typeof(int) }); //private static readonly MethodInfo isDBNullMethod = typeof(IDataRecord).GetMethod("IsDBNull", new [] { typeof(int) }); Populator<T> dynamicBuilder = new Populator<T>(); DynamicMethod method = new DynamicMethod("Create", typeof(T), new[] { typeof(Dictionary<string, object>) }, typeof(T), true); ILGenerator generator = method.GetILGenerator(); LocalBuilder result = generator.DeclareLocal(typeof(T)); generator.Emit(OpCodes.Newobj, typeof(T).GetConstructor(Type.EmptyTypes)); generator.Emit(OpCodes.Stloc, result); int i = 0; foreach (var property in properties) { PropertyInfo propertyInfo = typeof(T).GetProperty(property.Key, BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase | BindingFlags.FlattenHierarchy | BindingFlags.Default); Label endIfLabel = generator.DefineLabel(); if (propertyInfo != null && propertyInfo.GetSetMethod() != null) { generator.Emit(OpCodes.Ldarg_0); generator.Emit(OpCodes.Ldc_I4, i); //generator.Emit(OpCodes.Callvirt, isDBNullMethod); generator.Emit(OpCodes.Brtrue, endIfLabel); generator.Emit(OpCodes.Ldloc, result); generator.Emit(OpCodes.Ldarg_0); generator.Emit(OpCodes.Ldc_I4, i); //generator.Emit(OpCodes.Callvirt, getValueMethod); generator.Emit(OpCodes.Unbox_Any, property.Value.GetType()); generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod()); generator.MarkLabel(endIfLabel); } i++; } generator.Emit(OpCodes.Ldloc, result); generator.Emit(OpCodes.Ret); dynamicBuilder._handler = (Load)method.CreateDelegate(typeof(Load)); return dynamicBuilder; } } EDIT: Using Marc Gravell's PropertyDescriptor implementation (with HyperDescriptor) the code is simplified a hundred-fold. I now have the following test: using System; using System.Collections.Generic; using System.ComponentModel; using Hyper.ComponentModel; namespace Test { class Person { public int Id { get; set; } public string Name { get; set; } } class Program { static void Main() { HyperTypeDescriptionProvider.Add(typeof(Person)); var properties = new Dictionary<string, object> { { "Id", 10 }, { "Name", "Fred Flintstone" } }; Person person = new Person(); DynamicUpdate(person, properties); Console.WriteLine("Id: {0}; Name: {1}", person.Id, person.Name); Console.ReadKey(); } public static void DynamicUpdate<T>(T entity, Dictionary<string, object> properties) { foreach (PropertyDescriptor propertyDescriptor in TypeDescriptor.GetProperties(typeof(T))) if (properties.ContainsKey(propertyDescriptor.Name)) propertyDescriptor.SetValue(entity, properties[propertyDescriptor.Name]); } } } Any comments on performance considerations for both TypeDescriptor.GetProperties() & PropertyDescriptor.SetValue() are welcome...

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