{
	"@odata.context": "http://portal.xpertdoc.com/odata4/v6/$metadata#TemplateGroups/$entity",
	"TemplateGroupId": "00000000-0000-0000-0000-000000000000",
	"TemplateLibraryId": "00000000-0000-0000-0000-000000000000",
	"Name": "Name",
	"Description": null,
	"AddInContractName": "Xpertdoc.TemplateManager.Handler.TemplateDataProviders.XmlDataProvider",
	"AddInMetadata": null,
	"TemplateExecutionLabel": null,
	"Metadata": null,
	"UseParentDocumentOutputPostActions": true,
	"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": "AAAAAAAEqh8="
}

var templateGroup = portalContext.TemplateGroups.Where(tg => tg.TemplateGroupId == Guid.Parse("00000000-0000-0000-0000-000000000000")).FirstOrDefault();	

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

portalContext.UpdateObject(templateGroup);
portalContext.SaveChanges();