If you use EWS (Exchange Web Services) Managed API 1.0 or 1.1 beta, then its time for downloading its latest update: EWS Managed API 1.1 (Version 14.02.0051.000)

The Microsoft Exchange Web Services (EWS) Managed API 1.1 provides a managed interface for developing client applications that use Exchange Web Services. The EWS Managed API simplifies the implementation of applications that communicate with Microsoft Exchange Server 2007 Service Pack 1 (SP1) and later versions of Microsoft Exchange. Built on the Exchange Web Services SOAP protocol and Autodiscover, the EWS Managed API provides a .NET interface to EWS that is easy to learn, use, and maintain.

You can download it from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=c3342fb3-fbcc-4127-becf-872c746840e1

Note:
1) For x64 (64-bit) computers, download and run EwsManagedApi.msi
2) For x86 (32-bit) computers, download and run EwsManagedApi32.msi
3) Requires Microsoft .NET Framework 3.5 and Microsoft Visual Studio 2008 or later