To use the WSUS API, you need to reference the Update Services assembly. The assembly is found in the global assembly cache (GAC) at %windir%\Assembly\GAC_MSIL\Microsoft.UpdateServices.Administration\{version}\Microsoft.UpdateServices.Administration.dll.
程序集的位置是.....你是在什么平台下使用? .net吗? .net下需要添加程序集引用。