The concept of partial class has nothing to do with run time. The question makes no sense.
To understand what partial declaration does, read carefully:
http://msdn.microsoft.com/en-us/library/wa80x488.aspx[
^].
It looks like you do not really understand what a project build does, how the application is compiled, loaded and executed.
When you learn it, you will be able to pose the valid questions and learn the advanced matter that you may need.
Basically, you might need to implement and use some pluggability feature. Please see my past answers on the topic:
Create WPF Application that uses Reloadable Plugins...[
^],
AppDomain refuses to load an assembly[
^],
code generating using CodeDom[
^],
Create WPF Application that uses Reloadable Plugins...[
^],
Dynamically Load User Controls[
^],
C# Reflection InvokeMember on existing instance[
^],
Projects and DLL's: How to keep them managable?[
^].
You might also consider using MEF. Please see:
http://en.wikipedia.org/wiki/Managed_Extensibility_Framework[
^],
http://mef.codeplex.com/[
^].
It is possible that some simpler technique can suite your application goals, but then you would need to explain them properly. You would need some important skill of isolation of functional requirements from the possible technical solutions; that could help you to avoid loosing the ability to choose right solution due to wrong ideas you might be preoccupied with.
—SA