"Paul Welter" <pwelter@loresoft.com> wrote in message
news:Oa2UhSklFHA.572@TK2MSFTNGP15.phx.gbl...
> Is there anyway to do the following?
>
> Type myType = typeof(User);
> Collection<myType> list = new Collection<myType>();
>
> I know I could just use User instead of myType but have a function that
> takes a type and populates a collection then calls SetValue using
> reflection. How would I create the generic collection to fill it and call
> SetValue?
>

Paul Welter wrote:
> Is there anyway to do the following?
>
> Type myType = typeof(User);
> Collection<myType> list = new Collection<myType>();
>
> I know I could just use User instead of myType but have a function that
> takes a type and populates a collection then calls SetValue using
> reflection. How would I create the generic collection to fill it and call
> SetValue?

"Oliver Sturm" <oliver@sturmnet.org> wrote in message
news:u9jSs%23nlFHA.3660@TK2MSFTNGP10.phx.gbl...
> Paul Welter wrote:
>> Is there anyway to do the following?
>>
>> Type myType = typeof(User);
>> Collection<myType> list = new Collection<myType>();
>>
>> I know I could just use User instead of myType but have a function that
>> takes a type and populates a collection then calls SetValue using
>> reflection. How would I create the generic collection to fill it and
>> call SetValue?
>
> You can do this:
>
> Type genericType = typeof(Collection<>);
> Type constructedType = genericType.MakeGenericType(myType);
>
> Now you can create an instance of the constructed type and call methods on
> it via Reflection:
>
> object myObject = Activator.CreateInstance(constructedType, ...);
> myObject.GetType().InvokeMember("SetValue", BindingFlags.Instance |
> BindingFlags.InvokeMethod | BindingFlags.Public,
> null, myObject, new object[] { ... });
>
> Now finally, let me say this: I'm quite sure there should be a better way
> to do whatever it is exactly that you want to do. Especially since the
> advent of Generics... Think about it, or tell us about it.
>
>
> Oliver Sturm
> --
> omnibus ex nihilo ducendis sufficit unum
> Spaces inserted to prevent google email destruction:
> MSN oliver @ sturmnet.org Jabber sturm @ amessage.de
> ICQ 27142619 http://www.sturmnet.org/blog

"Paul Welter" <pwelter@loresoft.com> wrote in message
news:eFFgSQ6lFHA.3380@TK2MSFTNGP10.phx.gbl...
> Type.MakeGenericType works great, thanks. Couple question about
> MakeGenericType though. Is there a big performance hit for using
> Type.MakeGenericType? Is the performance hit in calling
> Type.MakeGenericType or when calling
> Activator.CreateInstance(constructedType, ...)? Would something be gained
> if I cached the Type output from the call to Type.MakeGenericType? I was
> thinking something like this ...
>
> private static Hashtable genericClassTypeCache =
> Hashtable.Synchronized(new Hashtable());
>
> private Type GetGenericClassType(Type classType, Type genericType)
> {
> string key = classType.ToString() + genericType.ToString();
> if (genericClassTypeCache.Contains(key))
> {
> return (Type)genericClassTypeCache[key];
> }
>
> Type constructedType = classType.MakeGenericType(genericType);
> genericClassTypeCache.Add(key, constructedType);
>
> return constructedType;
> }

Paul Welter wrote:

> Well, I'll answer this one myself. I did some simple performance testing
> and found that there was no difference between caching the type and just
> calling MakeGenericType every time. In the test I used 3 different generic
> collection types, 8 classes to use as the generic and ran it for about 200
> reps. The average time for calling MakeGenericType every time was 0.0156125
> milliseconds. The average time when using the caching function below was
> 0.018180451 milliseconds. I guess the runtime is doing its own caching, no
> need for it in this case. I would have thought there was going to be a
> bigger hit then that as generics are optimized at compile time.