好吧，我有一个非常可怕的方法可以做到。
您可以编写一个使用反射的方法（请耐心等待！）来计算特定类型的所有属性，并构建一个委托（使用 Reflection.Emit）将属性从该类型复制到另一个。然后使用匿名类型确保您只需要构建一次复制委托，因此速度很快。您的方法将如下所示：
public static Expression<Func<Foo, FooEditDto>> EditDtoSelector()
{
return f => MagicCopier<FooEditDto>.Copy(new {
f.PropertyA, f.PropertyB, f.PropertyC, f.PropertyD, f.PropertyC
});
}
这里的细微差别：
- MagicCopier 是泛型类型，Copy 是泛型方法，因此您可以显式指定“目标”类型，但隐式指定“源”类型。
- 它使用投影初始化器从用于初始化匿名类型的表达式中推断出属性的名称
我不确定它是否真的值得，但这是一个非常有趣的想法......无论如何我可能不得不实现它:)
编辑：使用MemberInitExpression，我们可以使用表达式树来完成这一切，这比 CodeDOM 容易得多。今晚试一试……
编辑：完成，它实际上是非常简单的代码。这是课程：
/// <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();
}
}
并称它为：
TargetType target = PropertyCopy<TargetType>.CopyFrom(new { First="Foo", Second="Bar" });