Act on Behalf of different user / XrmServiceContext.CallerID - asp.net-mvc-4

Question

I have created a XrmServiceContext using svcutil.exe for my CRM 2013 database, this is working great and I can retrieve data from CRM in my MVC4 application.
My website is running SSO using ADFS2 and I can retrieve the accessing users identity using:
Microsoft.IdentityModel.Claims.IClaimsIdentity ci = Thread.CurrentPrincipal.Identity as Microsoft.IdentityModel.Claims.IClaimsIdentity;
var accountNameClaim = ci.Claims.Where(x => x.ClaimType.ToLower().EndsWith("windowsaccountname")).FirstOrDefault();
this gives me something along the lines of
string accountNameClaim = "firstname.lastname#domain.com"
Using this I can retrieve the user form CRM 2013 XrmServiceContext
var user = _serviceContext.SystemUserSet
.Where( x=> x.DomainName == accountNameClaim)
.Select(s => new UserInformationProxy()
{
Id = s.Id, // this is probably needed for impersonation
FullName = s.FullName,
DomainName = s.DomainName
})
.FirstOrDefault();
Now I'm wondering how I act as / impersonate this user for all my subsequent queries to CRM using my XRMServiceContext.
This page http://msdn.microsoft.com/en-us/library/gg309629.aspx has a guide which suggests I need to set a variable called CallerID in OrganizationServiceContext which I'm guessing is contained somewhere inside my XRMServiceContext.. But I cannot find it.

Answer 1

The CallerId property is not on the OrganizationServiceContext but on the OrganizationServiceProxy that is used by the context:
When you are constructing the context, you are passing in an organization service intance. Prior to that, you need to set the CallerId:
organizationService.CallerId = user.Id;
var _serviceContext = new OrganizationServiceContext(organizationService);
Please note that the CallerId is only available on the OrganizationServiceProxy type, not on the interface IOrganiaztionService. I can't see how you obtain the organization service, but make sure it's an OrganizationServiceProxy.