[Solved]-Aggregating Lists inside of a List of objects using LINQ-LINQ,C#

// Get collection
var collection = _database.GetCollection<VehicleDataUpload>("Vehicles");

// Get first project that meets our identifier
var aggregation = collection
    .AsQueryable()
    // This will return an IEnumerable of Vehicles object
    .Where(i => i.ProjectId.Equals("1234"))
    // Assuming you want to return a plain list, you should use SelectMany
    .SelectMany(v => v.VehicleEntries
        // You group each list of VehicleEntries
        .GroupBy(ve => ve.Data)
        // For each group you return a new DailySummaryData object
        .Select(g => new DailySummaryData() {
            ProjectName = v.ProjectId,
            Date = g.Key,
            Passed = g.Sum(x => (x.VehicleStatus.Equals("PASSED") ? 1 : 0)),
            Failed = g.Sum(x => (x.VehicleStatus.Equals("FAILED") ? 1 : 0))
        })

return aggregation.ToList();