我需要将一个对象的某些属性复制到另一个对象。但是,某些属性需要从十进制到整数的类型转换。
我发现这个问题非常有用:将值从一个对象复制到另一个对象
但是,我不知道如何修改 Jon Skeet 和 Marc Gravell 的 MiscUtil 中的代码来检查属性类型以及源是否为十进制且目标是否为 int,以调用 Convert.ToIn32()。
这是 MiscUtil 的代码,我想弄清楚如何修改:
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();
}
}
}
}
如果你有
public class Foo
{
public decimal Value { get; set; }
}
public class Bar
{
public int Value { get; set; }
}
然后与自动映射器(可从 NuGet 获得)您可以将对象 Foo 映射到对象 Bar,如下所示:
Mapper.CreateMap<Foo, Bar>();
Foo foo = new Foo() { Value = 10.5M };
var bar = Mapper.Map<Bar>(foo);
// bar.Value = 10;
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