这是使用反射更新属性的最快方式吗?假设该属性始终为int类型:
PropertyInfo counterPropertyInfo = GetProperty();
int value = (int)counterPropertyInfo.GetValue(this, null);
counterPropertyInfo.SetValue(this, value + 1, null);
这是使用反射更新属性的最快方式吗?假设该属性始终为int类型:
PropertyInfo counterPropertyInfo = GetProperty();
int value = (int)counterPropertyInfo.GetValue(this, null);
counterPropertyInfo.SetValue(this, value + 1, null);
我在这里进行了一些基准测试,当你知道类型参数时(非泛型方法不会有太大区别)。如果无法直接访问属性,则CreateDelegate
是最快的方法。使用CreateDelegate
可以直接获取PropertyInfo
的GetGetMethod
和GetSetMethod
句柄,因此反射不会每次都被使用。
public static Func<S, T> BuildGetAccessor<S, T>(Expression<Func<S, T>> propertySelector)
{
return propertySelector.GetPropertyInfo().GetGetMethod().CreateDelegate<Func<S, T>>();
}
public static Action<S, T> BuildSetAccessor<S, T>(Expression<Func<S, T>> propertySelector)
{
return propertySelector.GetPropertyInfo().GetSetMethod().CreateDelegate<Action<S, T>>();
}
// a generic extension for CreateDelegate
public static T CreateDelegate<T>(this MethodInfo method) where T : class
{
return Delegate.CreateDelegate(typeof(T), method) as T;
}
public static PropertyInfo GetPropertyInfo<S, T>(this Expression<Func<S, T>> propertySelector)
{
var body = propertySelector.Body as MemberExpression;
if (body == null)
throw new MissingMemberException("something went wrong");
return body.Member as PropertyInfo;
}
现在你需要调用:
TestClass cwp = new TestClass();
var access = BuildGetAccessor((TestClass t) => t.AnyValue);
var result = access(cwp);
或者更好的方法是将逻辑封装在专用类中,以便在其中具有获取和设置方法。
就像这样:
public class Accessor<S>
{
public static Accessor<S, T> Create<T>(Expression<Func<S, T>> memberSelector)
{
return new GetterSetter<T>(memberSelector);
}
public Accessor<S, T> Get<T>(Expression<Func<S, T>> memberSelector)
{
return Create(memberSelector);
}
public Accessor()
{
}
class GetterSetter<T> : Accessor<S, T>
{
public GetterSetter(Expression<Func<S, T>> memberSelector) : base(memberSelector)
{
}
}
}
public class Accessor<S, T> : Accessor<S>
{
Func<S, T> Getter;
Action<S, T> Setter;
public bool IsReadable { get; private set; }
public bool IsWritable { get; private set; }
public T this[S instance]
{
get
{
if (!IsReadable)
throw new ArgumentException("Property get method not found.");
return Getter(instance);
}
set
{
if (!IsWritable)
throw new ArgumentException("Property set method not found.");
Setter(instance, value);
}
}
protected Accessor(Expression<Func<S, T>> memberSelector) //access not given to outside world
{
var prop = memberSelector.GetPropertyInfo();
IsReadable = prop.CanRead;
IsWritable = prop.CanWrite;
AssignDelegate(IsReadable, ref Getter, prop.GetGetMethod());
AssignDelegate(IsWritable, ref Setter, prop.GetSetMethod());
}
void AssignDelegate<K>(bool assignable, ref K assignee, MethodInfo assignor) where K : class
{
if (assignable)
assignee = assignor.CreateDelegate<K>();
}
}
简短而简单。您可以为每个“类属性”对携带一个此类的实例以进行获取/设置。
用法:
Person p = new Person { Age = 23 };
var ageAccessor = Accessor<Person>(x => x.Age);
int age = ageAccessor[p]; //gets 23
ageAccessor[p] = 45; //sets 45
这里对索引器的使用有些不太好,你可以用专门的“Get”和“Set”方法来替换它,但对我来说很直观 :)
为了避免每次都要指定类型,可以像下面这样:
var ageAccessor = Accessor<Person>(x => x.Age);
var nameAccessor = Accessor<Person>(x => x.Name);
var placeAccessor = Accessor<Person>(x => x.Place);
Accessor<>
类改变成可实例化的,这意味着你可以进行以下操作:var personAccessor = new Accessor<Person>();
var ageAccessor = personAccessor.Get(x => x.Age);
var nameAccessor = personAccessor.Get(x => x.Name);
var placeAccessor = personAccessor.Get(x => x.Place);
Accessor<>
类可以让您将它们视为一种类型,例如,var personAccessor = new Accessor<Person>();
var personAccessorArray = new Accessor<Person>[]
{
personAccessor.Get(x => x.Age),
personAccessor.Get(x => x.Name),
personAccessor.Get(x => x.Place);
};
Func<object, object>
和Action<object, object>
这样的getter和setter。 - nawfalAccessor<T>
数组而不会导致装箱惩罚,并稍后调用它。除非使用Func<S, object>
,否则无法为类创建通用的访问器集合。现在它不需要使用表达式树或反射,但我也展示了一种绕过GetValue
、SetValue
API的方法,使用表达式编译。正如我所说,将我的示例扩展到完全像动态访问器一样是微不足道的。 - nawfalFastMember
(nuget, 源代码),与反射相比,它真的很快。static long Benchmark(Action action, int iterationCount, bool print = true)
{
GC.Collect();
var sw = new Stopwatch();
action(); // Execute once before
sw.Start();
for (var i = 0; i <= iterationCount; i++)
{
action();
}
sw.Stop();
if (print) System.Console.WriteLine("Elapsed: {0}ms", sw.ElapsedMilliseconds);
return sw.ElapsedMilliseconds;
}
一个假的类:
public class ClassA
{
public string PropertyA { get; set; }
}
几个测试方法:
private static void Set(string propertyName, string value)
{
var obj = new ClassA();
obj.PropertyA = value;
}
private static void FastMember(string propertyName, string value)
{
var obj = new ClassA();
var type = obj.GetType();
var accessors = TypeAccessor.Create(type);
accessors[obj, "PropertyA"] = "PropertyValue";
}
private static void SetValue(string propertyName, string value)
{
var obj = new ClassA();
var propertyInfo = obj.GetType().GetProperty(propertyName);
propertyInfo.SetValue(obj, value);
}
private static void SetMethodInvoke(string propertyName, string value)
{
var obj = new ClassA();
var propertyInfo = obj.GetType().GetProperty(propertyName);
propertyInfo.SetMethod.Invoke(obj, new object[] { value });
}
脚本本身:
var iterationCount = 100000;
var propertyName = "PropertyA";
var value = "PropertyValue";
Benchmark(() => Set(propertyName, value), iterationCount);
Benchmark(() => FastMember(propertyName, value), iterationCount);
Benchmark(() => SetValue(propertyName, value), iterationCount);
Benchmark(() => SetMethodInvoke(propertyName, value), iterationCount);
100,000次迭代结果:
默认设置器: 3毫秒
FastMember: 36毫秒
PropertyInfo.SetValue: 109毫秒
PropertyInfo.SetMethod: 91毫秒
现在你可以自行选择!!!
FastMember
:-)。我使用BenchmakrDotNet将其与许多替代方案(如AutoMapper、CasltleDictionaryAdapter、缓存propertyInfo、缓存设置属性的操作以及手动编码的属性赋值)进行了比较。它只比直接属性分配慢36%,比下一个最快的替代方案快三倍。因此,我放弃了编写自己的代码,并将使用Marc的FastMember,感谢您!不错。 - Loudenvier请确保你以某种方式缓存了 PropertyInfo,以便不要多次调用 type.GetProperty。除此之外,如果你创建一个委托到类型上的方法来执行递增的操作,或者像 Teoman 建议的那样使类型实现一个接口并使用它,可能会更快。