Trying to use Group to get Max on two columns with Linq - sql

Question

I've been translating my programs to use Entity Framework 6 for the last two days. For the most part I have it down with simple CRUD operations. Today I hit a snag. I'm trying to convert;
Using SQLSERVER_Connection As New SqlConnection(GlobalVariables.SQLServer_Login_Details)
Using SQLCommand As New SqlCommand
Dim Command As New Text.StringBuilder
Command.AppendLine("SELECT TOP(1) EarningsYear AS PayYear, Max(EarningsAmt) AS EarnAmt, Max(Hours) AS HRS")
Command.AppendLine("FROM interview_payroll")
Command.AppendLine("GROUP BY CLIENTCODE, EarningsYear, SSN")
Command.AppendLine("HAVING CLIENTCODE = #CLIENTCODE AND SSN = #SSN ORDER BY EarningsYear DESC;")
SQLCommand.CommandText = Command.ToString
SQLCommand.Connection = SQLSERVER_Connection
SQLCommand.Parameters.Add("#CLIENTCODE", SqlDbType.VarChar).Value = sCLIENTCODE
SQLCommand.Parameters.Add("#SSN", SqlDbType.VarChar).Value = txtSSN.Text
SQLSERVER_Connection.Open()
Using Reader As SqlDataReader = SQLCommand.ExecuteReader()
While Reader.Read()
If Not IsDBNull(Reader("PayYear")) Then txtPayrollSourceDate.Text = CStr(Reader("PayYear"))
If Not IsDBNull(Reader("EarnAmt")) Then txtPayrollErnAmt.Text = CStr(Reader("EarnAmt"))
If Not IsDBNull(Reader("HRS")) Then txtPayrollHRS.Text = CStr(Reader("HRS"))
End While
End Using
SQLSERVER_Connection.Close()
End Using
End Using
into Linq.
I've got as far as;
Using DB As New wotcEntities
Dim Reader = From payroll In DB.interview_payroll
Where payroll.CONTROL = CONTROL And payroll.CLIENTCODE = sCLIENTCODE
Group payroll By payroll.CLIENTCODE, payroll.EarningsYear, payroll.SSN Into GPayroll = Group
End Using
But I just can't seem to jump the hurdle to get the MAX in EarningsAmt and Hours. I have this program called 'LINQ - Sample Queries' but it shows a MAX query as;
Public Sub LinqToSqlCount08()
Dim latestHire = Aggregate emp In db.Employees _
Into Max(emp.HireDate)
Console.WriteLine(latestHire)
End Sub
Which isn't going to work if I want to include PayYear.
I could just grab each part as separate queries, but that doesn't feel right.
How do I do this correctly?

Answer 1

I highly recommend the application "LINQPad". It can really help with writing queries and seeing the results immediately.
I created a table similar to what I could gather from your query, and was able to write this query which I believe does what you're asking for.
The "select" is where the Max aggregates are applied.
from payroll In Interview_payrolls
where payroll.CLIENTCODE = sClientCode
group payroll By payroll.CLIENTCODE, payroll.EarningsYear, payroll.SSN Into GPayroll = group
select PayYear = EarningsYear, EarnAmt = GPayroll.Max(Function(p) p.EarningsAmt), HRS = GPayroll.Max(Function(p) p.Hours)
Hope it works for you.