是否有一种方法可以为可观察的反应性扩展指定初始值?

In reactiveui and reactive extensions you can combine multiple observables into one. Using functions like CombineLatest or Zip you can make the resulting observable use a function to compute result based on values from combined observables. Though CombineLatest gives you an observable which gives you notifications each time any of the combined observables fires, it starts working only when all of those observables fires at least once. I want it to make notifications from the start - give combined observable an initial value, or something. Sure, I can somehow make those observable fire to set the initial values. But it is not that easy sometimes, or it makes the code look ugly. Here's an example: I'm making a wpf application using reactiveui. In one of my view models I'm trying to create properties by combining observables. So, I have a collection (ReactiveList) of objects with NumberToSum property, and I need a property that will be used to display the sum of that property values. Objects in that collection are also view models and their NumberToSum property can be changed by user. Number of objects taken for sum is determined by other property. That's how I tried to do it:In reactiveui and reactive extensions you can c