Activator.CreateInstance()和typeof(T).InvokeMember()与BindingFlags.CreateInstance之间的区别

Question

如果已经提出并回答了这个问题,请原谅我.

给定一类T型,下列之间有什么区别？

T myObj = Activator.CreateInstance<T>();

T myObj = typeof(T).InvokeMember(null, BindingFlags.CreateInstance, null, null, null);

一种解决方案比另一种优先吗？

Answer 1

反编译RuntimeType.InvokeMember产生这个片段:

if ((bindingFlags & BindingFlags.CreateInstance) != BindingFlags.Default)
{
    if (((bindingFlags & BindingFlags.CreateInstance) != BindingFlags.Default) && ((bindingFlags & (BindingFlags.SetProperty | BindingFlags.GetProperty | BindingFlags.SetField | BindingFlags.GetField | BindingFlags.InvokeMethod)) != BindingFlags.Default))
    {
        throw new ArgumentException(Environment.GetResourceString("Arg_CreatInstAccess"), "bindingFlags");
    }
    return Activator.CreateInstance(this, bindingFlags, binder, providedArgs, culture);
}

换句话说,InvokeMember那些BindingFlags电话Activator.CreateInstance.在开始业务之前,它会经历几个调用层(检查绑定,验证参数).Activator.CreateInstance<T>更简洁:

public static T CreateInstance<T>()
{
    bool bNeedSecurityCheck = true;
    bool canBeCached = false;
    RuntimeMethodHandle emptyHandle = RuntimeMethodHandle.EmptyHandle;
    return (T) RuntimeTypeHandle.CreateInstance(typeof(T) as RuntimeType, true, true, ref canBeCached, ref emptyHandle, ref bNeedSecurityCheck);
}

编辑你可能会认为后者更快,但是一个叫做的方法RuntimeType.CreateInstanceSlow也叫做RuntimeTypeHandle.CreateInstance工作; 如果找不到构造函数的Activator缓存条目,它将用作后备.如果你正在寻找两者中最快的解决方案,我会做一些性能测试.