CQLinq query could be like following:
let totalLinesSum = JustMyCode.Methods.Where(t => t.IsPublic).Sum(t => t.NbLinesOfCode)
let methodsCount = JustMyCode.Methods.Where(t => t.IsPublic).Count()
let result = (double)totalLinesSum / methodsCount
select (double?)result
...or a bit more refined, this query can be refactored like:
// Let define your methods set the way you need
// It is worth removing abstract method that have no LoC
let methodsSet = JustMyCode.Methods.Where(m => m.IsPublic && !m.IsAbstract)
let totalLoc = methodsSet.Sum(t => t.NbLinesOfCode)
let methodsCount = methodsSet.Count()
let avgLoc = (double)totalLoc / methodsCount
select (double?)avgLoc