When the map first comes up at Full Extent only some of the features display
I need a feature class because I need the "Where" method.
Do you mean that the full extent is not the right one (i.e. there are features outside of the full extent) or that some features are not visible despite they are supposed to be in the current extent?
If your map service is not cached, you might also use a map service layer definition to filter the objects (just another option, faeture layer shoud work as well).
Its just missing alot of features when I use the featurelayer.
How do you set the layer definition on the ArcGISDynamicMapServiceLayer? What method? Do you have an simple code example?