C#高性能动态获取对象属性值的步骤

时间:2021-05-20

动态获取对象的性能值,这个在开发过程中经常会遇到,这里我们探讨一下何如高性能的获取属性值。为了对比测试,我们定义一个类People

public class People{ public string Name { get; set; }}

然后通过直接代码调用方式来取1千万次看要花多少时间:

private static void Directly(){ People people = new People { Name = "Wayne" }; Stopwatch stopwatch = Stopwatch.StartNew(); for (int i = 0; i < 10000000; i++) { object value = people.Name; } stopwatch.Stop(); Console.WriteLine("Directly: {0}ms", stopwatch.ElapsedMilliseconds);}

大概花了37ms:

反射
通过反射来获取对象的属性值,这应该是大家常用的方式,但这种方式的性能比较差。接下来我们来看看同样取1千万次需要多少时间:

private static void Reflection(){ People people = new People { Name = "Wayne" }; Type type = typeof(People); PropertyInfo property = type.GetProperty("Name"); Stopwatch stopwatch = Stopwatch.StartNew(); for (int i = 0; i < 10000000; i++) { object value = property.GetValue(people); } stopwatch.Stop(); Console.WriteLine("Reflection: {0}ms", stopwatch.ElapsedMilliseconds);}

大概花了1533ms,果然要慢很多:

那既然反射慢,那还有没有其它方式呢?

动态构建Lambda
我们知道可以动态构建Linq的Lambda表达式,然后通过编译后得到一个委托,如果能动态构建返回属性值的委托,就可以取到值了。所以我们想办法构建一个像这样的委托:

Func<People, object> getName = m => m.Name;

接下来我们就通过Expression来构建:

private static void Lambda(){ People people = new People { Name = "Wayne" }; Type type = typeof(People); var parameter = Expression.Parameter(type, "m");//参数m PropertyInfo property = type.GetProperty("Name"); Expression expProperty = Expression.Property(parameter, property.Name);//取参数的属性m.Name var propertyDelegateExpression = Expression.Lambda(expProperty, parameter);//变成表达式 m => m.Name var propertyDelegate = (Func<People, object>)propertyDelegateExpression.Compile();//编译成委托 Stopwatch stopwatch = Stopwatch.StartNew(); for (int i = 0; i < 10000000; i++) { object value = propertyDelegate.Invoke(people); } stopwatch.Stop(); Console.WriteLine("Lambda:{0}ms", stopwatch.ElapsedMilliseconds);}

然后我们测试一下,大概花了138ms,性能要比反射好非常多:

委托调用

虽然动态构建Lambda的性能已经很好了,但还是更好吗?毕竟比直接调用还是差了一些,要是能直接调用属性的取值方法就好了。

在C#中,可读属性都有一个对应的get_XXX()的方法,可以通过调用这个方法来取得对应属性的值。可以使用System.Delegate.CreateDelegate创建一个委托来调用这个方法。

  • 通过委托调用方法来取得属性值

我们定义一个MemberGetDelegate的委托,然后通过它来调用取值方法:

delegate object MemberGetDelegate(People p);private static void Delegate(){ People people = new People { Name = "Wayne" }; Type type = typeof(People); PropertyInfo property = type.GetProperty("Name"); MemberGetDelegate memberGet = (MemberGetDelegate)System.Delegate.CreateDelegate(typeof(MemberGetDelegate), property.GetGetMethod()); Stopwatch stopwatch = Stopwatch.StartNew(); for (int i = 0; i < 10000000; i++) { object value = memberGet(people); } stopwatch.Stop(); Console.WriteLine("Delegate: {0}ms", stopwatch.ElapsedMilliseconds);}

然后我们测试一下,大概花了38ms,性能几乎与直接调用一致:

最后做一个简单的封装,缓存一下创建的Delegate

public class PropertyValue<T>{ private static ConcurrentDictionary<string, MemberGetDelegate> _memberGetDelegate = new ConcurrentDictionary<string, MemberGetDelegate>(); delegate object MemberGetDelegate(T obj); public PropertyValue(T obj) { Target = obj; } public T Target { get; private set; } public object Get(string name) { MemberGetDelegate memberGet = _memberGetDelegate.GetOrAdd(name, BuildDelegate); return memberGet(Target); } private MemberGetDelegate BuildDelegate(string name) { Type type = typeof(T); PropertyInfo property = type.GetProperty(name); return (MemberGetDelegate)Delegate.CreateDelegate(typeof(MemberGetDelegate), property.GetGetMethod()); }}

这样使用起来就方便多了

People people = new People { Name = "Wayne" };PropertyValue<People> propertyValue = new PropertyValue<People>(people);object value = propertyValue.Get("Name");

以上就是C#高性能动态获取对象属性值的步骤的详细内容,更多关于c# 获取对象属性值的资料请关注其它相关文章!

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