WorkOnBehalfOf
The WorkOnBehalfOf property of the Context object is used in the special cases where one user is running the service methods, but the security privileges for a second user should be used. The WorkOnBehalfOf property will be set to the login name for this second user.
Warning: For typical web service calls, you shouldn't set this property. It should be set only in the special cases where one web service user is performing actions on behalf of a different user.
The value for the property will have the following form:
DOMAIN\USERNAME
or
COMPUTERNAME\USERNAME
Refer to Working on behalf of another user for more details about the special situations where the property is used.