PROSAGA码农传奇-C#/.net-预编译的lambda表达式创建具有带参数的构造函数的类

<div class =“post-text”itemprop =“text”>
  
    实际上，使用
     <code>
 Expression.Compile
 </code>
     将是
    
      慢点
    
     如果你只需要创建
    
      一
    
     宾语。但是，如果你缓存创建者函数，从长远来看它会更快，因为lambda性能会很好。
  
  
    这是代码：
  
   <pre>
 <code>
 static Func<TArg, T> CreateCreator<TArg, T>()
{
 var constructor = typeof(T).GetConstructor(new Type[] { typeof(TArg) });
 var parameter = Expression.Parameter(typeof(TArg), "p");
 var creatorExpression = Expression.Lambda<Func<TArg, T>>(
 Expression.New(constructor, new Expression[] { parameter }), parameter);
 return creatorExpression.Compile();
}

</code>
 </pre>
   <pre>
 <code>
 Func<TArg, T> creator = CreateCreator<TArg, T>();

</code>
 </pre>
  
    有了这个，你可以使用
     <code>
 creator(arg)
 </code>
     用于创建新对象
     <code>
 T
 </code>
    。
  
  <HR />
  
    三种方式的小基准：
  
   <pre>
 <code>
 class Program
{
 static void Main(string[] args)
 {
 // warm up
 Test1<Class1>(0);
 Test2<int, Class1>(0);

const int numiter = 10000;
 var sw1 = Stopwatch.StartNew();
 for (int i = 0; i < numiter; i++)
 Test1<Class1>(i);
 sw1.Stop();
 Console.WriteLine($"With Activator.CreateInstance: " +
 $"{(double)sw1.ElapsedTicks / numiter} ticks per object");

var sw2 = Stopwatch.StartNew();
 for (int i = 0; i < numiter; i++)
 Test2<int, Class1>(i);
 sw2.Stop();

Console.WriteLine($"With Expression.Compile: " +
            $"{(double)sw2.ElapsedTicks / numiter} ticks per object");

var sw3 = Stopwatch.StartNew();
 var creator = CreateCreator<int, Class1>();
 for (int i = 0; i < numiter; i++)
 creator(i);
 sw3.Stop();

Console.WriteLine($"With cached Expression.Compile: " +
            $"{(double)sw3.ElapsedTicks / numiter} ticks per object");
    }

static public object Test1<T>(params object[] parameters)
 {
 var instance = (T)Activator.CreateInstance(
 typeof(T), BindingFlags.Instance | BindingFlags.Public, null, parameters, null);
 return instance;
 }

static Func<TArg, T> CreateCreator<TArg, T>()
 {
 var constructor = typeof(T).GetConstructor(new Type[] { typeof(TArg) });
 var parameter = Expression.Parameter(typeof(TArg), "p");
 var creatorExpression = Expression.Lambda<Func<TArg, T>>(
 Expression.New(constructor, new Expression[] { parameter }), parameter);
 return creatorExpression.Compile();
 }

static public object Test2<TArg, T>(TArg arg)
 {
 var creator = CreateCreator<TArg, T>();
 return creator(arg);
 }
}

</code>
 </pre>
  
    在我的机器上生成以下结果（发布模式/ Visual Studio外部）：
  
   <pre class="lang-none prettyprint-override">
 <code>
 With Activator.CreateInstance: 3.0739 ticks per object
With Expression.Compile: 494.0388 ticks per object
With cached Expression.Compile: 0.1097 ticks per object

</code>
 </pre>
</DIV>