how to use Linq groupby and where with date conditions in vb.net

I'm trying to use Linq groupby and where with date conditions in vb.net

Please Guide Me.

PIQ is total purchase quantity

SIQ is total sales quantity

BLC is total purchase quantity minus total sales quantity

Thanks

Public Class Form3    Private Purchase, Sales As New List(Of Invoice)    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load        LoadData()    End Sub    Private PurchaseDetails,SalesDetails As New List(Of Detail)    Private Function CreateConnection() As String        Return ("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\TRIAL2.accdb;Persist Security Info=False;")    End FunctionPrivate Sub LoadData()        Using Connection = New OleDbConnection(CreateConnection()) Purchase = CType(Connection.Query(Of Invoice)("SELECT * FROM PURCHASE"), List(Of Invoice))            PurchaseDetails = CType(Connection.Query(Of Detail)("SELECT * FROM PURCHASEDETAILS"), List(Of Detail)) Sales = CType(Connection.Query(Of Invoice)("SELECT * FROM SALES"), List(Of Invoice))            SalesDetails = CType(Connection.Query(Of Detail)("SELECT * FROM SALESDETAILS"), List(Of Detail))End Using        Dim ps = From p In Purchase                 Where p.DATEINVO >= CDate("01/01/2024")                 From pd In PurchaseDetails                 Select             pd.ITEM,             PIQ = pd.QTY,             SIQ = 0,             BLC = pd.QTY                 Order By ITEM        Dim ss = From s In Sales                 Where s.DATEINVO >= CDate("01/01/2024")                 From sd In SalesDetails                 Select            sd.ITEM,            PIQ = 0,            SIQ = sd.QTY,            BLC = -sd.QTY                 Order By ITEM Dim Card_temp = ps.Union(ss).OrderBy(Function(w) w.ITEM) Dim Card As New List(Of ItemCards3)        Dim RunningBalance As Integer = 0        For Each ct In Card_temp            Dim sc As New ItemCards3            With sc                .ITEM = ct.ITEM                .PIQ = ct.PIQ                .SIQ = ct.SIQ                .BLC = RunningBalance + ct.BLC                RunningBalance = .BLC            End With            Card.Add(sc)        Next        DataGridView1.DataSource = Card    End SubEnd ClassPublic Class Invoice    Property INVONO() As String    Property DATEINVO() As Date    Property CUSTCODE() As StringEnd ClassPublic Class Detail    Public Property INVONO() As String    Public Property NOD() As Integer    Public Property ITEM() As String    Public Property QTY() As IntegerEnd ClassPublic Class ItemCards3    Public Property ITEM() As String    Public Property PIQ As Integer    Public Property SIQ As Integer    Public Property BLC As IntegerEnd Class

Table PURCHASE

Table PURCHASEDETAILS

Table SALES

Table SALESDETAILS

the result of the code above

Desired result