{
	"@odata.context": "http://portal.xpertdoc.com/odata4/v6/$metadata#UserProfiles/$entity",
	"@odata.etag": "0000000000000000000000000000000000",
	"UserProfileId": "00000000-0000-0000-0000-000000000000",
	"Name": "username",
	"Roles": null,
	"FirstName": "John",
	"LastName": "Doe",
	"Email": "[email protected]",
	"CultureLcid": 4105,
	"TimeZone": "Eastern Standard Time",
	"IsSystem": false,
	"CreatedByUserProfileId": "00000000-0000-0000-0000-000000000000",
	"CreatedDate": "2016-01-01T00:00:00.0000000Z",
	"ModifiedByUserProfileId": "00000000-0000-0000-0000-000000000000",
	"ModifiedDate": "2016-01-01T00:00:00.0000000Z",
	"Timestamp": "AAAAAAAByp4="
}

var userProfile = portalContext.UserProfiles.Where(up => up.UserProfileId == Guid.Parse("00000000-0000-0000-0000-000000000000")).FirstOrDefault();	

userProfile.Name = "New Name";
userProfile.ValueToChange = value;

portalContext.UpdateObject(userProfile);
portalContext.SaveChanges();