How to read data from a nested select query linq - linq

Question

I have a query like the following which is of type linq.
var querymiangin = (from t1 in _context.Apiapplicant
join t2 in _context.ApiApplicantHistory on t1.Id equals t2.ApiApplicantId
join t3 in _context.EntityType on t2.LastReqStatus equals t3.Id
where t1.IsDeleted == false && t1.LastRequestStatus == t2.Id && t3.Name == "granted"
select new { A = t1, B = t2, Year = t1.ApiRequestDate.Substring(0, 4), Month = t1.ApiRequestDate.Substring(5, 2) } into joined
group joined by new { joined.Year, joined.Month, joined.B.LastReqStatus } into grouped
select grouped.Select(g => new { ApiReqDate = g.A.ApiRequestDate, ApiDate = g.B.Date, ApiLastReqStatus = g.B.LastReqStatus, ApiYear = g.Year, ApiMonth = g.Month })).ToList();
In the select part, ApiReqDate and ApiDate has multiple records. Now my problem is for each group of month and year, I have multiple ApiDate and ApiReqDate records and I want for each group based on a condition (t1.LastRequestStatus == t2.Id && t3.Name == "granted") by using GetPersianDaysDiffDate() method, obtain the difference between ApiReqDate and its related ApiDate records for each month and then find their average in that month.
For doing that, I have written code like this:
var avgDateDiff = querymiangin.DefaultIfEmpty()
.GroupBy(x => new { x.ApiYear, x.ApiMonth }, (key, g) => new
{
key.ApiYear,
key.ApiYear,
Avg = g.Average(y => GetPersianDaysDiffDate(y.ApiReqDate,y.ApiDate))
})
.ToList();
But the problem is each parameter x.ApiYear, x.ApiMonth,y.ApiReqDate,y.ApiDate are unknown and it shows me error. I appreciate if anyone can suggest me a solution for that.

Answer 1

1 - For the first request querymiangin, you don't need to group by statement, change little the code to :
var querymiangin = (from t1 in Apiapplicant
join t2 in ApiApplicantHistory on t1.Id equals t2.ApiApplicantId
join t3 in EntityType on t2.LastReqStatus equals t3.Id
where t1.IsDeleted == false && t1.LastRequestStatus == t2.Id && t3.Name == "granted"
select new
{
ApiReqDate = t1.ApiRequestDate,
ApiDate = t2.Date,
ApiYear = t1.ApiRequestDate.Substring(0, 4),
ApiMonth = t1.ApiRequestDate.Substring(5, 2)
}).ToList();
2 - For the second query avgDateDiff, use GroupBy by ApiYear and ApiMonth and calculate the Average, like :
var avgDateDiff = querymiangin
.GroupBy(x => new { x.ApiYear, x.ApiMonth }, (key, g) => new
{
key.ApiYear,
key.ApiMonth,
Avg = g.Average(y => GetPersianDaysDiffDate(y.ApiReqDate, y.ApiDate))
}).ToList();
I hope you find this helpful.