I am a newbie in Lync and currently developing an application by Lync UCMA 4.0. But when I add reference Microsoft.Rtc.Collaboration and using Microsoft.Rtc.Collaboration.Sample.Common; occured error:
The type of namespace 'Sample' does not exist in the namespace 'Microsoft.Rtc.Collaboration' (Are you missing an assembly reference?)
I had added
Microsoft.Rtc.Collaboration
I guess you are following an example as Sample.Common is not a member of the Microsoft.Rtc.common namespace.
The Sample.Common namespace appears in a number of Microsoft example and is usually created as part of the tutorial.
Have a look at the following for a code listing for UCMAHelper class in the Sample.Common namespace https://msdn.microsoft.com/en-us/library/office/hh527753(v=office.14).aspx