将属性值从一个对象自动应用到同一类型的另一个对象？
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给定2个类型为T的对象A和B，我想将A中的属性值分配给B中的相同属性，而不对每个属性进行显式赋值。
我想保存这样的代码：
b.Nombre = a.Nombre;
b.Descripcion = a.Descripcion;
b.Imagen = a.Imagen;
b.Activo = a.Activo;
做某事
a.ApplyProperties(b);
可能吗？
答案
我在MiscUtil中有一个名为PropertyCopy的类型，它做了类似的事情 - 虽然它创建了一个新的目标类型实例并将属性复制到其中。
它不要求类型相同 - 它只是将所有可读属性从“源”类型复制到“目标”类型。当然，如果类型相同，那更有可能工作:)这是一个浅层副本，顺便说一句。
在本答案底部的代码块中，我扩展了该类的功能。要从一个实例复制到另一个实例，它在执行时使用简单的PropertyInfo值 - 这比使用表达式树慢，但另一种方法是编写一个动态方法，我不太热。如果表现对你来说绝对至关重要，请告诉我，我会看到我能做些什么。要使用该方法，请编写如下内容：
MyType instance1 = new MyType();
// Do stuff
MyType instance2 = new MyType();
// Do stuff
PropertyCopy.Copy(instance1, instance2);
（其中Copy是一种使用类型推断的通用方法）。
我还没准备好完成一个完整的MiscUtil版本，但这里是更新的代码，包括注释。我不会为SO编辑器重新编写它们 - 只需复制整个块。
（如果我从头开始，我也可能在命名方面重新设计API，但我不想打破现有用户......）
#if DOTNET35
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
namespace MiscUtil.Reflection
{
/// <summary>
/// Non-generic class allowing properties to be copied from one instance
/// to another existing instance of a potentially different type.
/// </summary>
public static class PropertyCopy
{
/// <summary>
/// Copies all public, readable properties from the source object to the
/// target. The target type does not have to have a parameterless constructor,
/// as no new instance needs to be created.
/// </summary>
/// <remarks>Only the properties of the source and target types themselves
/// are taken into account, regardless of the actual types of the arguments.</remarks>
/// <typeparam name="TSource">Type of the source</typeparam>
/// <typeparam name="TTarget">Type of the target</typeparam>
/// <param name="source">Source to copy properties from</param>
/// <param name="target">Target to copy properties to</param>
public static void Copy<TSource, TTarget>(TSource source, TTarget target)
where TSource : class
where TTarget : class
{
PropertyCopier<TSource, TTarget>.Copy(source, target);
}
}
/// <summary>
/// Generic class which copies to its target type from a source
/// type specified in the Copy method. The types are specified
/// separately to take advantage of type inference on generic
/// method arguments.
/// </summary>
public static class PropertyCopy<TTarget> where TTarget : class, new()
{
/// <summary>
/// Copies all readable properties from the source to a new instance
/// of TTarget.
/// </summary>
public static TTarget CopyFrom<TSource>(TSource source) where TSource : class
{
return PropertyCopier<TSource, TTarget>.Copy(source);
}
}
/// <summary>
/// Static class to efficiently store the compiled delegate which can
/// do the copying. We need a bit of work to ensure that exceptions are
/// appropriately propagated, as the exception is generated at type initialization
/// time, but we wish it to be thrown as an ArgumentException.
/// Note that this type we do not have a constructor constraint on TTarget, because
/// we only use the constructor when we use the form which creates a new instance.
/// </summary>
internal static class PropertyCopier<TSource, TTarget>
{
/// <summary>
/// Delegate to create a new instance of the target type given an instance of the
/// source type. This is a single delegate from an expression tree.
/// </summary>
private static readonly Func<TSource, TTarget> creator;
/// <summary>
/// List of properties to grab values from. The corresponding targetProperties
/// list contains the same properties in the target type. Unfortunately we can't
/// use expression trees to do this, because we basically need a sequence of statements.
/// We could build a DynamicMethod, but that's significantly more work :) Please mail
/// me if you really need this...
/// </summary>
private static readonly List<PropertyInfo> sourceProperties = new List<PropertyInfo>();
private static readonly List<PropertyInfo> targetProperties = new List<PropertyInfo>();
private static readonly Exception initializationException;
internal static TTarget Copy(TSource source)
{
if (initializationException != null)
{
throw initializationException;
}
if (source == null)
{
throw new ArgumentNullException("source");
}
return creator(source);
}
internal static void Copy(TSource source, TTarget target)
{
if (initializationException != null)
{
throw initializationException;
}
if (source == null)
{
throw new ArgumentNullException("source");
}
for (int i = 0; i < sourceProperties.Count; i++)
{
targetProperties[i].SetValue(target, sourceProperties[i].GetValue(source, null), null);
}
}
static PropertyCopier()
{
try
{
creator = BuildCreator();
initializationException = null;
}
catch (Exception e)
{
creator = null;
initializationException = e;
}
}
private static Func<TSource, TTarget> BuildCreator()
{
ParameterExpression sourceParameter = Expression.Parameter(typeof(TSource), "source");
var bindings = new List<MemberBinding>();
foreach (PropertyInfo sourceProperty in typeof(TSource).GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
if (!sourceProperty.CanRead)
{
continue;
}
PropertyInfo targetProperty = typeof(TTarget).GetProperty(sourceProperty.Name);
if (targetProperty == null)
{
throw new ArgumentException("Property " + sourceProperty.Name + " is not present and accessible in " + typeof(TTarget).FullName);
}
if (!targetProperty.CanWrite)
{
throw new ArgumentException("Property " + sourceProperty.Name + " is not writable in " + typeof(TTarget).FullName);
}
if ((targetProperty.GetSetMethod().Attributes & MethodAttributes.Static) != 0)
{
throw new ArgumentException("Property " + sourceProperty.Name + " is static in " + typeof(TTarget).FullName);
}
if (!targetProperty.PropertyType.IsAssignableFrom(sourceProperty.PropertyType))
{
throw new ArgumentException("Property " + sourceProperty.Name + " has an incompatible type in " + typeof(TTarget).FullName);
}
bindings.Add(Expression.Bind(targetProperty, Expression.Property(sourceParameter, sourceProperty)));
sourceProperties.Add(sourceProperty);
targetProperties.Add(targetProperty);
}
Expression initializer = Expression.MemberInit(Expression.New(typeof(TTarget)), bindings);
return Expression.Lambda<Func<TSource, TTarget>>(initializer, sourceParameter).Compile();
}
}
}
#endif
另一答案
几年来，我正在使用一个名为ValueInjecter的流行库
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