How to change value of a cell in datagrid in WPF (C# or VB.NET)

Private Sub DGEmployeeList_AddingNewItem(sender As Object, e As AddingNewItemEventArgs) Handles DGEmployeeList.AddingNewItem
    ' Create a new Employee instance for your new item
    Dim newEmployee As New Employee()

    ' Check if there are existing items in the EmployeeList, in your case there are 2
    If EmployeeList.Count > 0 Then
        ' If there are existing items, calculate the maximum index number by finding the maximum value of the IndexNo property among the existing items, starting at 0
        newEmployee.IndexNo = EmployeeList.Max(Function(emp) emp.IndexNo) + 1 'This will returm 3 in your case
    Else
        ' If there are no existing items, set the index number to 0
        newEmployee.IndexNo = 0
    End If

    ' Add the newEmployee to the EmployeeList
    'EmployeeList.Add(newEmployee) Not required as we already added a new employee, use when required.

    ' Set the new item as the added item in the event arguments
    e.NewItem = newEmployee
End Sub

Imports System.Collections.ObjectModel

Class MainWindow
    Sub New()
        InitializeComponent()

        ' Create an instance of the ObservableEmployeeList here instead of List(Of Employee)
        EmployeeList = New ObservableCollection(Of Employee)()

        ' Add the initial employee data
        EmployeeList.Add(New Employee With {
            .IndexNo = 1,
            .employeeID = 7354,
            .employeeName = "John Smith",
            .employeeAddress = "122 made up Lane",
            .employeeCity = "Cameden",
            .employeeState = "New Jersey"
        })

        EmployeeList.Add(New Employee With {
            .IndexNo = 2,
            .employeeID = 9456,
            .employeeName = "Andy Coesfoe",
            .employeeAddress = "345 Green Street",
            .employeeCity = "Salt Lake",
            .employeeState = "Utah"
        })

        DGEmployeeList.ItemsSource = EmployeeList
    End Sub

    Partial Class Employee
        Public Property IndexNo As Integer
        Public Property employeeID As Integer
        Public Property employeeName As String
        Public Property employeeAddress As String
        Public Property employeeCity As String
        Public Property employeeState As String
    End Class

    ' Use ObservableCollection(Of T) instead of List(Of T)
    Public EmployeeList As ObservableCollection(Of Employee)

    Private Sub DGEmployeeList_AddingNewItem(sender As Object, e As AddingNewItemEventArgs) Handles DGEmployeeList.AddingNewItem
        ' Create a new Employee instance for the new item
        Dim newEmployee As New Employee()

        If EmployeeList.Count > 0 Then
            newEmployee.IndexNo = EmployeeList.Max(Function(emp) emp.IndexNo) + 1
        Else
            newEmployee.IndexNo = 0
        End If

        ' Add the newEmployee to the EmployeeList
        'EmployeeList.Add(newEmployee) Not required as we already added a new employee, use when required.

        ' Set the new item as the added item in the event arguments
        e.NewItem = newEmployee
    End Sub
End Class

Imports System.Collections.ObjectModel
Imports System.ComponentModel

Class MainWindow
    Sub New()
        InitializeComponent()

        'Create an instance of the ObservableEmployeeList instead of List(Of Employee)
        EmployeeList = New ObservableCollection(Of Employee)()
        
        EmployeeList.Add(New Employee With {
            .IndexNo = 1,
            .employeeID = 7354,
            .employeeName = "John Smith",
            .employeeAddress = "122 made up Lane",
            .employeeCity = "Camden",
            .employeeState = "New Jersey"
        })

        EmployeeList.Add(New Employee With {
            .IndexNo = 2,
            .employeeID = 9456,
            .employeeName = "Andy Coesfoe",
            .employeeAddress = "345 Green Street",
            .employeeCity = "Salt Lake",
            .employeeState = "Utah"
        })

        'Set the ItemsSource of the DataGrid to a ListCollectionView
        Dim view As ListCollectionView = New ListCollectionView(EmployeeList)
        view.SortDescriptions.Add(New SortDescription("IndexNo", ListSortDirection.Ascending))
        DGEmployeeList.ItemsSource = view

        'Subscribe to CollectionChanged event to handle changes to the EmployeeList
        AddHandler EmployeeList.CollectionChanged, AddressOf EmployeeList_CollectionChanged
    End Sub

    Partial Class Employee
        Public Property IndexNo As Integer
        Public Property employeeID As Integer
        Public Property employeeName As String
        Public Property employeeAddress As String
        Public Property employeeCity As String
        Public Property employeeState As String
    End Class

    'Use ObservableCollection(Of T) instead of List(Of T)
    Public EmployeeList As ObservableCollection(Of Employee)

    Private Sub EmployeeList_CollectionChanged(sender As Object, e As System.Collections.Specialized.NotifyCollectionChangedEventArgs)
        'This event handler will be called whenever the EmployeeList changes, such as adding or removing an item.

        'Update the IndexNo property for each item in the EmployeeList
        Dim newIndex As Integer = 1
        For Each emp As Employee In EmployeeList
            emp.IndexNo = newIndex
            newIndex += 1
        Next
    End Sub

    Private Sub DGEmployeeList_AddingNewItem(sender As Object, e As AddingNewItemEventArgs) Handles DGEmployeeList.AddingNewItem
        'Create a new Employee instance for the new item
        Dim newEmployee As New Employee()

        If EmployeeList.Count > 0 Then
            'If there are existing items, calculate the maximum index number
            'by finding the maximum value of the IndexNo property among the existing items
            newEmployee.IndexNo = EmployeeList.Max(Function(emp) emp.IndexNo) + 1
        Else
            'If there are no existing items, set the index number to 1
            newEmployee.IndexNo = 1
        End If

        'Add the newEmployee to the EmployeeList
        EmployeeList.Add(newEmployee)

        'Set the new item as the added item in the event arguments
        e.NewItem = newEmployee
    End Sub
End Class