brady gaster

Be aware of the fact that Activator.CreateInstance() most likely uses reflection, which can be slow.

You can also consider a factory pattern implementation.

Small perf. gain there ;)

oh yeah, teensy. itsy-bitsy. weenie-teenie.

and thanks frans. i think i'm going to couple your comment with another i received from the original posting and create yet one more example.

Can you post the exact code you benchmarked with? I'd like to see the code that gives some a vast difference between the methods

I wrote my own benchmark...


Type type = typeof(Person);
ConstructorInfo ctor = type.GetConstructor(Type.EmptyTypes);

StopWatch sw = new StopWatch();
for (int a = 0; a < 3; a++)
{
for (int i = 0; i < 1000000; i++)
{
Person person = (Person) ctor.Invoke(null);
}
Console.WriteLine("Objects Created: " + Person.getCount());
Console.WriteLine("Execution Time: " + sw.ElapsedMilliseconds());
sw.Reset();
}

for (int a = 0; a < 3; a++)
{
for (int i = 0; i < 1000000; i++)
{
Person person = (Person) Activator.CreateInstance(type);
}
Console.WriteLine("Objects Created: " + Person.getCount());
Console.WriteLine("Execution Time: " + sw.ElapsedMilliseconds());
sw.Reset();
}

for (int a = 0; a < 3; a++)
{
for (int i = 0; i < 1000000; i++)
{
Person person = (Person) ClassLoader.newInstance(type);
}
Console.WriteLine("Objects Created: " + Person.getCount());
Console.WriteLine("Execution Time: " + sw.ElapsedMilliseconds());
sw.Reset();
}



StopWatch is a wrapper class to the win32 performance timers.


the first loop runs on invoking an already constructed ConstructorInfo object.

Second is Activator,

third is my caching ClassLoader object:

public static Object newInstance(Type type)
{
if (type == null)
throw new ApplicationException("Type supplied cannot be null");

string key = type.FullName;

ConstructorInfo ctor = cache[key] as ConstructorInfo;
if (ctor == null)
{
ctor = type.GetConstructor(Type.EmptyTypes);
cache[key] = ctor;
}
return ctor.Invoke(null);
}

here is the output:


Objects Created: 1000000
Execution Time: 681.5
Objects Created: 2000000
Execution Time: 659.9
Objects Created: 3000000
Execution Time: 668.5
Objects Created: 4000000
Execution Time: 1136.6
Objects Created: 5000000
Execution Time: 1193.8
Objects Created: 6000000
Execution Time: 1160.7
Objects Created: 7000000
Execution Time: 1058.3
Objects Created: 8000000
Execution Time: 1070
Objects Created: 9000000
Execution Time: 1072.6


as you can see.. the constructorinfo invoke method is the fastest, followed by the cached constructorinfo, flowed closely by Activator.CreateInstance....

given the fact that the difference in speed between the two latter methods is minimal, you may as well just use Activator.CreateInstance, and save yourself some programming/worry