LINQ: GroupBy, Sum and EntityCollection in CRM

Just sharing a sample code that could be used for group by and sum operation on EntityCollection.

Suppose below is the output that we want

We can use the below code for that.

// select categoryid, final forecast, final awards from SubCategory Entity
// category id is lookup in SubCategory Entity

EntityCollection result = orgProxy.RetrieveMultiple(new FetchExpression(fetch));

var details = from r in result.Entities.AsEnumerable()
group r by new
{
groupByCategoryID = ((EntityReference)r.Attributes["categoryId"]).Id.ToString()
}
into g
select new
{
sumFinalForecast = g.Sum(x => Convert.ToInt32(x.Attributes["finalforecast"])),
sumFinalAwards = g.Sum(x => Convert.ToInt32(x.Attributes["finalawards"])),
categoryId = g.Key.groupByCategoryID
};

// update the parent record
foreach(var detail in details)
{
Entity entityUpdate = new Entity("category");
entityUpdate.Id = new Guid(detail.categoryId);
entityUpdate.Attributes["totalfinalforecast"] = detail.sumFinalForecast;
entityUpdate.Attributes["totalfinalawards"] = detail.sumFinalAwards;
orgProxy.Update(entityUpdate);
}

Hope it helps..