public async Task CreateAsync(T entity)
{
var existing = await this.GetAsync(entity.Id);
if (existing != null)
{
throw new InvalidOperationException(
string.Format("The {0} with user id {1} and id {2} already exists", typeof(T), entity.SaveItUserId, entity.Id));
}
db.GetEntitySet <T>().Add(entity);
}
