Add ToAsync functions

[Bezarius]

• Func<T, IObservable> ToAsync<T, TResult>(Func<T, TResult> function)
• Func<T, IObservable> ToAsync<T, TResult>(Func<T, TResult> function, IScheduler scheduler)
• Func<T1, T2, IObservable> ToAsync<T1, T2, TResult>(Func<T1, T2, TResult> function)
• Func<T1, T2, IObservable> ToAsync<T1, T2, TResult>(Func<T1, T2, TResult> function, IScheduler scheduler)
• Func<T1, T2, T3, IObservable> ToAsync<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function)
• Func<T1, T2, T3, IObservable> ToAsync<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function, IScheduler scheduler)
• Func<T1, T2, T3, T4, IObservable> ToAsync<T1, T2, T3, T4, TResult>(Func<T1, T2, T3, T4, TResult> function)
• Func<T1, T2, T3, T4, IObservable> ToAsync<T1, T2, T3, T4, TResult>(Func<T1, T2, T3, T4, TResult> function, IScheduler scheduler)
• Func<T1, T2, IObservable> ToAsync<T1, T2>(Action<T1, T2> action)
• Func<T1, T2, IObservable> ToAsync<T1, T2>(Action<T1, T2> action, IScheduler scheduler)
• Func<T1, T2, T3, IObservable> ToAsync<T1, T2, T3>(Action<T1, T2, T3> action)
• Func<T1, T2, T3, IObservable> ToAsync<T1, T2, T3>(Action<T1, T2, T3> action, IScheduler scheduler)
• Func<T1, T2, T3, T4, IObservable> ToAsync<T1, T2, T3, T4>(Action<T1, T2, T3, T4> action)
• Func<T1, T2, T3, T4, IObservable> ToAsync<T1, T2, T3, T4>(Action<T1, T2, T3, T4> action, IScheduler scheduler)

Run a method asynchronously on demand

Execute a long-running method asynchronously. The method does not start running until there is a subscriber. The method is started every time the observable is created and subscribed, so there could be more than one running at once.

// Synchronous operation
public DataType DoLongRunningOperation(string param)
{
    ...
}

public IObservable<DataType> LongRunningOperationAsync(string param)
{
    return Observable.Create<DataType>(
        o => Observable.ToAsync<string,DataType>(DoLongRunningOperation)(param).Subscribe(o)
    );
}