我试图执行乔恩斯基特对解决这个问题，在此发布的博客文章来替代SetValue使用委托非反射法的方法。
从解决方案的差异博客文章是SetValue是void ，而我得到的The type 'System.Void' may not be used as a type argument. 在该行例外MethodInfo miConstructedHelper = miGenericHelper.MakeGenericMethod(typeof(G), pMethod.GetParameters()[0].ParameterType, pMethod.ReturnType); 。
下面是我实现的MagicMethod ：
public class Instantiator<T> where T : new()
{
private T instance;
private IDictionary<string, PropertyInfo> properties;
private Func<PropertyInfo, object, object> _fncSetValue;
public Instantiator()
{
Type type = typeof(T);
properties = type.GetProperties().GroupBy(p => p.Name).ToDictionary(g => g.Key, g => g.ToList().First());
MethodInfo miSetValue = typeof(PropertyInfo).GetMethod("SetValue", new Type[] { typeof(object), typeof(object), typeof(object[]) });
_fncSetValue = SetValueMethod<PropertyInfo>(miSetValue);
}
public void CreateNewInstance()
{
instance = new T();
}
public void SetValue(string pPropertyName, object pValue)
{
if (pPropertyName == null) return;
PropertyInfo property;
if (!properties.TryGetValue(pPropertyName, out property)) return;
TypeConverter tc = TypeDescriptor.GetConverter(property.PropertyType);
//substitute this line
//property.SetValue(instance, tc.ConvertTo(pValue, property.PropertyType), null);
//with this line
_fncSetValue(property, new object[] { instance, tc.ConvertTo(pValue, property.PropertyType), null });
}
public T GetInstance()
{
return instance;
}
private static Func<G, object, object> SetValueMethod<G>(MethodInfo pMethod) where G : class
{
MethodInfo miGenericHelper = typeof(Instantiator<T>).GetMethod("SetValueMethodHelper", BindingFlags.Static | BindingFlags.NonPublic);
MethodInfo miConstructedHelper = miGenericHelper.MakeGenericMethod(typeof(G), pMethod.GetParameters()[0].ParameterType, pMethod.ReturnType);
object retVal = miConstructedHelper.Invoke(null, new object[] { pMethod });
return (Func<G, object, object>) retVal;
}
private static Func<TTarget, object, object> SetValueMethodHelper<TTarget, TParam, TReturn>(MethodInfo pMethod) where TTarget : class
{
Func<TTarget, TParam, TReturn> func = (Func<TTarget, TParam, TReturn>)Delegate.CreateDelegate(typeof(Func<TTarget, TParam, TReturn>), pMethod);
Func<TTarget, object, object> retVal = (TTarget target, object param) => func(target, (TParam) param);
return retVal;
}
}
您正在使用Func在你的代码。 Func是有一个返回类型的方法。 对于返回方法void ，你需要使用Action 。
你的代码需要看起来像这样：
public class Instantiator<T> where T : new()
{
private T instance;
private IDictionary<string, PropertyInfo> properties;
private Action<PropertyInfo, object, object, object> _fncSetValue;
public Instantiator()
{
Type type = typeof(T);
properties = type.GetProperties()
.GroupBy(p => p.Name)
.ToDictionary(g => g.Key, g => g.ToList().First());
var types = new Type[] { typeof(object), typeof(object),
typeof(object[]) };
var miSetValue = typeof(PropertyInfo).GetMethod("SetValue", types);
_fncSetValue = SetValueMethod<PropertyInfo>(miSetValue);
}
public void CreateNewInstance()
{
instance = new T();
}
public void SetValue(string pPropertyName, object pValue)
{
if (pPropertyName == null) return;
PropertyInfo property;
if (!properties.TryGetValue(pPropertyName, out property)) return;
TypeConverter tc = TypeDescriptor.GetConverter(property.PropertyType);
var value = tc.ConvertTo(pValue, property.PropertyType);
_fncSetValue(property, instance, value, null);
}
public T GetInstance()
{
return instance;
}
private static Action<G, object, object, object> SetValueMethod<G>(MethodInfo pMethod) where G : class
{
var miGenericHelper =
typeof(Instantiator<T>).GetMethod("SetValueMethodHelper",
BindingFlags.Static |
BindingFlags.NonPublic);
var parameters = pMethod.GetParameters();
var miConstructedHelper = miGenericHelper.MakeGenericMethod(typeof(G),
parameters[0].ParameterType,
parameters[1].ParameterType,
parameters[2].ParameterType);
var retVal = miConstructedHelper.Invoke(null, new object[] { pMethod });
return (Action<G, object, object, object>) retVal;
}
private static Action<TTarget, object, object, object> SetValueMethodHelper<TTarget, TParam1, TParam2, TParam3>(MethodInfo pMethod) where TTarget : class
{
var func = (Action<TTarget, TParam1, TParam2, TParam3>)Delegate.CreateDelegate(typeof(Action<TTarget, TParam1, TParam2, TParam3>), pMethod);
Action<TTarget, object, object, object> retVal =
(target, param1, param2, param3) =>
func(target, (TParam1) param1, (TParam2) param2, (TParam3) param3);
return retVal;
}
}
当你不想打电话给像乔恩斯基特任意方法，则可以简化你的代码了很多 。 没有必要为一个呼叫MethodInfo.Invoke在你的代码，因为这是没有必要的代表。 你可以简单地调用SetValue对返回的直接PropertyInfo 。 有没有必要使用委托，反过来反正调用正是方法的弯路。 此外，如类型转换是不必要SetValue需要一个object反正。
你的代码可能是这么简单：
public class SimpleInstantiator<T> where T : new()
{
private T instance;
private IDictionary<string, PropertyInfo> properties;
public SimpleInstantiator()
{
Type type = typeof(T);
properties = type.GetProperties()
.GroupBy(p => p.Name)
.ToDictionary(g => g.Key, g => g.ToList().First());
}
public void CreateNewInstance()
{
instance = new T();
}
public void SetValue(string pPropertyName, object pValue)
{
if (pPropertyName == null) return;
PropertyInfo property;
if (!properties.TryGetValue(pPropertyName, out property)) return;
property.SetValue(instance, pValue, null);
}
public T GetInstance()
{
return instance;
}
}
性能测试结果表明，该版本只需要大约50％的前一个。
在性能上一个微小的增加是由于这样的事实，我们避免了我们在电话链上的两个不必要的代表。 然而，绝大多数的速度的提高奠定了在我们删除了类型转换的事实。
