I have a list of keyvaluepair(string,string) first string is something like class.property, second string is the value to assign to that class.property.
I'm currently looping through that list and by using reflection I set every value.
it work, but my question is there a faster way to do this?
If you're using the same property repeatedly (e.g. against a variety of target objects), it's faster to build a delegate out of the setter using Delegate.CreateDelegate and use that. However, I'd only do that when I'd profiled it and found that this was a bottleneck. It happened to make a big difference against my protocol buffer implementation, but that really needs to be as fast as possible, so I'm happy to apply a bit of micro-optimisation.
If you need to set the same property, or properties on the same type, more than once, cache your Type and PropertyInfo's. It is very easy stuff to cache - and examining the types is what typically takes the time in reflection scenarios.
If you can use C# 4 for this, you might be able to come up with a faster solution using dynamic. (I have seen the .NET 3.5 tag, just thought I would mention it).
If all items in your list of properties are known, and of a rather manageable size, you could make a switch for it. The code would be less clean, but easier to understand and quicker to execute. Since they're strings in the input-end, both approaches are as prone to human error.