Question

有人建议将一个对象的值映射到另一个对象吗？我想要一个使用反射的实用程序类，如果有一个具有相同名称的公共属性，它将获取两个对象并将值从第一个对象复制到第二个对象。

我有两个从Web服务代理生成的实体，所以我不能更改父类或者修改接口或类似的东西。但我知道这两个对象具有相同的公共属性。

Answer 1

一起扔起来应该很简单......

public static void CopyPropertyValues(object source, object destination)
{
    var destProperties = destination.GetType().GetProperties();

    foreach (var sourceProperty in source.GetType().GetProperties())
    {
        foreach (var destProperty in destProperties)
        {
            if (destProperty.Name == sourceProperty.Name && 
        destProperty.PropertyType.IsAssignableFrom(sourceProperty.PropertyType))
            {
                destProperty.SetValue(destination, sourceProperty.GetValue(
                    source, new object[] { }), new object[] { });

                break;
            }
        }
    }
}

Answer 2

Jon Skeet和Marc Gravell有一个名为MiscUtil的图书馆。在MiscUtil.Reflection内，有一个名为PropertyCopy的类，它完全按照您的描述进行操作。它仅适用于.NET 3.5。

它的工作原理是遍历SourceType的公共属性，通过名称与TargetType的公共属性进行匹配，确保每个属性都可以从源分配到目标，然后创建并缓存复制器功能对于这两种类型（所以你不是每次都做这些反射）。我已经在生产代码中使用它并且可以保证它的优点。

嘿，我想我只是发布他们的简洁代码（不到100行/评论）。可以在here找到此代码的许可证：

using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;

namespace MiscUtil.Reflection
{
    /// <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>.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.
        /// </summary>
        private static class PropertyCopier<TSource> where TSource : class
        {
            private static readonly Func<TSource, TTarget> copier;
            private static readonly Exception initializationException;

            internal static TTarget Copy(TSource source)
            {
                if (initializationException != null)
                {
                    throw initializationException;
                }
                if (source == null)
                {
                    throw new ArgumentNullException("source");
                }
                return copier(source);
            }

            static PropertyCopier()
            {
                try
                {
                    copier = BuildCopier();
                    initializationException = null;
                }
                catch (Exception e)
                {
                    copier = null;
                    initializationException = e;
                }
            }

            private static Func<TSource, TTarget> BuildCopier()
            {
                ParameterExpression sourceParameter = Expression.Parameter(typeof(TSource), "source");
                var bindings = new List<MemberBinding>();
                foreach (PropertyInfo sourceProperty in typeof(TSource).GetProperties())
                {
                    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.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)));
                }
                Expression initializer = Expression.MemberInit(Expression.New(typeof(TTarget)), bindings);
                return Expression.Lambda<Func<TSource,TTarget>>(initializer, sourceParameter).Compile();
            }
        }
    }
}

Answer 3

我们使用Automapper。它的效果非常好。

Answer 4

我已经改进了Robinson的答案并将其重构为Object类型的扩展方法，非常方便：

    public static void CopyPropertyValues( this object destination, object source )
    {
        if ( !( destination.GetType ().Equals ( source.GetType () ) ) )
            throw new ArgumentException ( "Type mismatch" );
        if ( destination is IEnumerable )
        {
            var dest_enumerator = (destination as IEnumerable).GetEnumerator();
            var src_enumerator = (source as IEnumerable).GetEnumerator();
            while ( dest_enumerator.MoveNext () && src_enumerator.MoveNext () )
                dest_enumerator.Current.CopyPropertyValues ( src_enumerator.Current );
        }
        else
        {
            var destProperties = destination.GetType ().GetRuntimeProperties ();
            foreach ( var sourceProperty in source.GetType ().GetRuntimeProperties () )
            {
                foreach ( var destProperty in destProperties )
                {
                    if ( destProperty.Name == sourceProperty.Name 
                        && destProperty.PropertyType.GetTypeInfo ()
                            .IsAssignableFrom ( sourceProperty.PropertyType.GetTypeInfo () ) )
                    {
                        destProperty.SetValue ( destination, sourceProperty.GetValue (
                            source, new object[] { } ), new object[] { } );
                        break;
                    }
                }
            }
        }
    }

Answer 5

我在Marc Gravell阅读using Expression<T> to do this后不久发表了关于this article的博文。

它看起来（根据另一个答案）可能类似于Jon Skeet和Marc的MiscUtil中的那个。

Answer 6

用Json.net做什么呢？

static T CopyPropertiesJson<T>(object source)
{
    string jsonsource = JsonConvert.SerializeObject(source);
    return JsonConvert.DeserializeObject<T>(jsonsource);
}

将值从一个对象复制到另一个对象

6 个答案: