C#高性能动态获取对象属性值的步骤-C/C++开发

这篇文章主要介绍了C#高性能动态获取对象属性值的步骤，帮助大家更好的理解和使用c#，感兴趣的朋友可以了解下

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:


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：


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：


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：


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");

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