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Hi guys.
When I click on empty part of datagrid, it adds new line to enter new data. So I need to change the first value as automated number as index of datas. I mean for example if the datagrid has 2 lines of datas, when adding new line, the item INDEX should be 3 automatically.
How can I do that?

What I have tried:

Bellow are the codes:

XML
<Window x:Class="MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp4"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid Margin="10">
        <DataGrid x:Name="DGEmployeeList"
            HorizontalAlignment="Stretch"
            VerticalAlignment="Stretch"
            HorizontalContentAlignment="Stretch"
            VerticalContentAlignment="Stretch"
            CanUserAddRows="True"
            CanUserDeleteRows="True"
            CanUserResizeColumns="True"
            CanUserReorderColumns="True"
            CanUserSortColumns="True"
            IsTextSearchEnabled="True"
            SelectionMode="Single"
            SelectionUnit="CellOrRowHeader"
            AutoGenerateColumns="False"
            >
            <DataGrid.Columns>
                <DataGridTextColumn Header="INDEX" IsReadOnly="True" Width="Auto" Binding="{Binding IndexNo}"/>
                <DataGridTextColumn Header="ID" IsReadOnly="False" Width="Auto" Binding="{Binding employeeID}"/>
                <DataGridTextColumn Header="NAME" IsReadOnly="False" Width="Auto" Binding="{Binding employeeName}"/>
                <DataGridTextColumn Header="ADDRESS" IsReadOnly="False" Width="Auto" Binding="{Binding employeeAddress}"/>
                <DataGridTextColumn Header="CITY" IsReadOnly="False" Width="Auto" Binding="{Binding employeeCity}"/>
                <DataGridTextColumn Header="STATE" IsReadOnly="False" Width="Auto" Binding="{Binding employeeState}"/>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>


VB.NET
Class MainWindow
    Sub New()
        InitializeComponent()
        EmployeeList.Add(New Employee With {
                        .IndexNo = 1,
                        .employeeID = 7354,
                        .employeeName = "John Smith",
                        .employeeAddress = "122 made up Lane",
                        .employeeCity = "Cameden",
                        .employeeState = "New Jersy"
                        })

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

        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
    Public EmployeeList As New System.Collections.Generic.List(Of Employee)

    Private Sub DGEmployeeList_AddingNewItem(sender As Object, e As AddingNewItemEventArgs) Handles DGEmployeeList.AddingNewItem
        sender.item(0) = EmployeeList(sender.item(0)).IndexNo - 1
    End Sub

End Class
Posted
Updated 17-Jul-23 0:01am
v4
Comments
Graeme_Grant 15-Jul-23 19:43pm    
Learn to use data binding, then you don't work directly on the datagrid, you work on the collection behind the datagrid. The datagrid is then a "view" of the data.
Sh.H. 15-Jul-23 23:47pm    
@Graeme_Grant Thanks for reply. The DataGrid is bind with a list(of ). So I tried to edit item on the list in the handler, while clicking on the Datagrid to edit. It sends an exception that I cannot edit list which is binded to the datagrid.
Anyway. Could please help me on this? When I click to edit datagrid, I want to autofill some cells, like the cell which indicates the index.
Graeme_Grant 16-Jul-23 7:10am    
If you're using data binding, then you should have the DataContext set to an ObservableCollection. You should not be using events like that.
Ralf Meier 16-Jul-23 8:41am    
Perhaps (but I'm not sure) your mistake is that you try to change the item and not it's value - that depends perhaps on the type of the elements of your List.
You should provide more Info - also what kind of exeption do you get and where ...?
Sh.H. 17-Jul-23 3:42am    
@Graeme_Grant
@Ralf Meier
Thanks for reply. I added all codes of solution. Please see the main post again. Thanks.

for to be able to answer your question it's necessary to privide more info (as allready mentioned by me).

But to your Code-Snippet :
Inside a List of whatever there is NO index -1. You try to assign the index -1 to the index 0 from your List !!!

Independant from that : what kind of type are the items of the List ?
 
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Comments
Sh.H. 17-Jul-23 3:42am    
@Ralf Meier
Thanks for reply. I added all codes of solution. Please see the main post again. Thanks.
Ralf Meier 17-Jul-23 4:20am    
... but now the original Code is gone ... lets go back to there because there is the part which throws the exception because you make a complete wrong assignment. Please improve this question with that code and perhaps made corrections ...
Sh.H. 17-Jul-23 4:28am    
Updated. I added the handler sub.
Ralf Meier 17-Jul-23 4:41am    
back to your method :
sender is an object - if you want to use it you must at first assign it to a variable which type it the original type of the sender - in your case Employee. Object is the base-type from variables and it doesn't consists of items and so on - it's more or less a kind of pointer ...
This is a very common task that can be answered via a Google Search: wpf tutorial datagrid edit - Google Search[^]

There are many answers and YouTube videos that discuss how to do this. Here are some:
* How to - Implement editing functionality - Windows Community Toolkit | Microsoft Learn[^]
* C# - WPF Desktop App - Edit Employees (DataGrid & Row Double Click Event) - YouTube[^]
* The DataGrid control - The complete WPF tutorial[^]

If you want others, click on the Google Search Link[^] and look at others.

UPDATE
I have not fired up VS, so these are just observations.

DataBinding WITH Collections
The DataGrid listens to the ICollectionChanged and INotifyPropertyChanged events. The List does not have these events. There is a specialized collection called the ObservableCollection that does support these events. This was mentioned yesterday in the comments above.

Use the right tool for the job - you don't use a hammer for removing screws, you use a screwdriver. If you ask for help, then take the time to read the help given.

Again, I don't post links for the sake of looking good, I post them as they will benefit you. I've taken the time to try and help, you need to take the time to look and learn.
 
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v3
Comments
Ralf Meier 17-Jul-23 4:24am    
of course all your links are very useful for the OP - but I suppose the problem he has is using the List and especially the items in it in the wrong way.
Graeme_Grant 17-Jul-23 4:29am    
There is a lot wrong there, hence the links to try and straighten him out. He needs to invest the time.
Sh.H. 17-Jul-23 4:33am    
What do you mean by a lot wrong? If you see anything wrong, please kindly do me favor and let me know. Thanks.
Graeme_Grant 17-Jul-23 4:37am    
Yesterday, I pointed out a key issue and what you should be doing. Today, I provided links to resources that will answer this better than I can here in Quick Answers. This is my pointer to help you.

As a bonus, you are trying to use Data Binding with WPF however you're struggling. Here is a link that explains how it works in detail. Take the time to read and learn: Data binding overview - WPF .NET Framework | Microsoft Learn[^]
Ralf Meier 17-Jul-23 4:38am    
complete agree with you ... but I suppose we are (he is) lightyears away from using the binding ...
Based on the links given by Graeme (you should read an entire tutorial, not just the top part), use an 'if' statement to check if there are any employees added to the list, if not your index will be '0', if there are, count the items and add 1 to the count which will give you the proper index number -

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


[EDIT]
If the above code error with message - 'System.Invalid.Operation: An ItemsControl is inconsistent with its item source', it means that the exception encountered is caused by attempting to modify the EmployeeList directly while it is bound to the DataGrid. To overcome this error, you can use an 'ObservableCollection(Of T)' instead of a 'List(Of T)' for EmployeeList - MS Learn ObservableCollection<t> Class[^]

You can adapt your code to -
VB.NET
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


[EDIT 2]
Based on comments below regarding the update of 'IndexNo' when a row is delted -

To handle a row that were deleted, you can listen to the 'CollectionChanged' event of the 'ObservableCollection' and reassign the correct index values to each item whenever a change occurs. Alternatively, you can use a 'ListCollectionView' to sort the collection based on the 'IndexNo' property.

Your code will look similar to -
VB.NET
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
 
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v5
Comments
Graeme_Grant 17-Jul-23 5:21am    
Hand a man a fish, you feed him for a day. Teach him to fish, you feed him for a lifetime.

The OP seems to rely heavily on asking questions here for simple things. I could have posted an answer like the above, and in the past I have. I thought it was time to take the next step and show how to learn.

I have not tried your answer but it sounds okay. +5 ... I have not checked, but I still think that an ObserveableCollection is required for the data binding for the collection change to appear in the DataGrid.
Sh.H. 17-Jul-23 5:27am    
@Andre Oosthuizen
Thank for code.
Unfortunately didn't work.
This is the exception after double clicking on a cell to add new data.
https://ibb.co/xF4Kw6K
Ralf Meier 17-Jul-23 8:44am    
... and your actual code is ...?
Have you took a look with the Debugger to see what is happening inside your code ?
Andre Oosthuizen 17-Jul-23 5:38am    
Thanks Graeme, I've checked the profile, yup, almost pointing to 'help-vampire', I should have checked. Thanks for the up's!
Andre Oosthuizen 17-Jul-23 5:45am    
@Sh.H, please see Graeme's comment, you need to learn to give proper information, show some real effort from your side. Your comment just now is a very good example of how NOT to do it, show the error, don't just post a screen shot, I almost decided not to open the link! and it points to laziness. When you encountered the error, show us what you did to try and resolve the error. See my updated answer in the post.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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