I have got an error that is
'The type or namespace 'Xrm' does not exist in the namespace 'Microsoft''.
I've already added Microsoft.Xrm.Sdk.dll. My project's Framework version is Framework 4.5. I added .dll from CRM 2015 SDK folder. Why is that occured? Thanks for helps !
The project's Framework version needs to be 4.5.2.
Although, that is a compiler error, you may need to remove the reference and add it again.