>I mean i download the other people project , then this project create dll....... So i want to improve the project...
>In this time , I opne my project and plus in this project and dll , and set the project some breakpoint .....
>1 question, The project breakpoint no interrupt...

So you have the full source for the project and you have added that project to your solution?
If that is the case then you should only need to ensure that the relevant project is generating debug information.
In the Solution property page (for the Active configuration):
Check that the Configuration setting for the project is 'Debug'
In the Project property page / Compile tab:
Select the Debug configuration and, in the Advanced Compiler Options.. window make sure 'Generate debug info' is 'Full'

>2. question, In this time , i only one method to change other people project first to create the dll... After, i take
>the dll to my project... but i everytime change i will overwrite the dll..... But i already add the other people project ,
>then two project , what can't i immediately improve project code....must everytime over the dll?

Sorry, I do not understand....