How to Put New Row at Top of DataGrid

Hi, @RogerSchlueter-7899. Welcome to Microsoft Q&A. 

You could insert data to the top of DataGrid using DataTable.Rows.InsertAt(newRow,0);

Reference sample code

MainWindow.xaml

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="3*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <DataGrid x:Name="MyDataGrid" RowEditEnding="MyDataGrid_RowEditEnding">
            
        </DataGrid>
        <Button Grid.Row="1" Width="200" Content="Add NewRow"  Height="50" Click="Button_Click"></Button>
    </Grid>

MainWindow.xaml.cs

    public partial class MainWindow : Window
    {
        DataTable dt = new DataTable();
        public MainWindow()
        {
            InitializeComponent();

            //Defining initial data
            dt.Columns.Add("Column1");
            dt.Columns.Add("Column2");

            dt.Rows.Add("Row1Column1", "Row1Column2");
            dt.Rows.Add("Row2Column1", "Row2Column2");

            //Binding
            MyDataGrid.ItemsSource = dt.DefaultView;
            var i = (IEditableCollectionView)MyDataGrid.Items;
            i.NewItemPlaceholderPosition = NewItemPlaceholderPosition.AtBeginning;

        }

        //Adding New Data
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            DataRow newRow = dt.NewRow();
            newRow["Column1"] = "Row3Column1";
            newRow["Column2"] = "Row4Column1";
            dt.Rows.InsertAt(newRow,0);
        }

        private void MyDataGrid_RowEditEnding(object sender, DataGridRowEditEndingEventArgs e)
        {
            var dataGrid = sender as DataGrid;
            var collectionView = (IEditableCollectionView)dataGrid.Items;

            if (collectionView.IsAddingNew)
            {
                // Get the DataRowView of the new row
                var newItem = collectionView.CurrentAddItem as DataRowView;

                if (newItem != null)
                {
                    // Complete the adding operation
                    collectionView.CommitNew();

                    // Get the bound DataTable
                    var dataTable = ((DataView)dataGrid.ItemsSource).Table;

                    if (dataTable != null)
                    {
                        // Insert a new row at the top of the DataTable
                        var newRow = newItem.Row;
                        dataTable.Rows.Remove(newRow); // Remove the current line first
                        dataTable.Rows.InsertAt(newRow, 0); // Insert at top
                    }
                }
            }
        }

    }

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