我可以使用.net 3.5二进制文件用于具有.net 4.0应用程序的库/如果有的话是什么？

Can I use .net 3.5 binaries for a library with a .net 4.0 application / what are the negatives if any? In other words is there any reason I should take more time out to download source for the library and build it under .net 4.0 (assuming it builds without any problems I guess) as opposed to downloading the .net 3.5 binaries. Can I use .net 3.5 binaries for a library with