Could not load file or assembly 'Microsoft.Xrm.Client

Could not load file or assembly 'Microsoft.Xrm.Client

I have created a plug-in in CRM. It's registered successfully. Inside my
plug-in I have created a web service with many functions. After successful
calling of plug-in step I am getting error-
System.IO.FileNotFoundException: Could not load file or assembly
'Microsoft.Xrm.Client, Version=5.0.9689.2166, Culture=neutral,
PublicKeyToken=31bf3856ad364e35' or one of its dependencies`. The system
cannot find the file specified. To solve this issue I have created the New
XRM.cs file from crmsvcutil.exe but got the same issue. Searched more
about this but no solutions found yet.
NOTE: I am using the Microsoft hosted version of CRM
Here below the reference files which I am using.
microsoft.crm.sdk.proxy
Microsoft.CSharp
microsoft.xrm.client
microsoft.xrm.portal
microsoft.xrm.sdk
System
System System.Core
System.Data
System.Data.Services
System.Data.Services.Client
System.DirectoryServices.AccountManagement
System.Runtime.Serialization
System.ServiceModel
System.Xml
System.Xml.Linq
Is there any way to run my plugin on Hosted version of CRM???
Appreciate if any help :)