对于这两者的不同，MSDN的解释如下

• IExecutionContext.UserId Property: Gets the global unique identifier of the system user for whom the plug-in
invokes Web service methods on behalf of. ^[1]

• IExecutionContext.InitiatingUserId: Gets the global unique identifier of the system user account under which the current pipeline is executing. ^[2]

^{字面上的理解，前者即插件的调用者，后者即当前管道的执行者}

^{歪国友人针对这个问题做的实验如下，通过实验可以加深你的理解}

^{http://www.magnetismsolutions.com/blog/zhenyuwang/2012/7/7/the_difference_between_userid_and_initiatinguserid_in_plugin_of_dynamic_crm_2011}