How to refresh/ reload all the items in a WPF datagrid

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C#

.NET

WPF

I am fetching details from a sql database and am showing them in datagrid as shown below.

using (SqlConnection con = new SqlConnection(UserIDDataTableConnString))
{
    SqlCommand cmd = new SqlCommand("select * from TBL_TicketMngr where Status = 'Follow Up';", con);
    con.Open();
    SqlDataAdapter sda = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable("TBL_TicketMngr");
    sda.Fill(dt);
    DG_FollowUp.ItemsSource = dt.DefaultView;
}

XAML of datagrid:

<DataGrid Name="DG_FollowUp"  AutoGenerateColumns="False" SelectionMode="Single" SelectedIndex="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Column="0" Grid.Row="01" BorderBrush="Black" BorderThickness="0.5" LoadingRow="DG_FollowUp_LoadingRow" IsEnabled="True" IsReadOnly="True" AlternationCount="2" ><!--VirtualizingStackPanel.IsVirtualizing="True"-->
                    <datagrid.columns>                       
                        <DataGridTextColumn Binding="{Binding [TicketID/Subject]}" Header="TicketID/Subject" Width="300" CanUserSort="False"/>
                        <DataGridTextColumn Binding="{Binding [AddDate]}" Header="Start Date" Width="90" CanUserSort="False">
                        <DataGridTextColumn Binding="{Binding [Status]}" Header="Status" Width="80" CanUserSort="False">
                        <DataGridTextColumn Binding="{Binding [OwnerShip]}" Header="Ownership" Width="130" CanUserSort="False">
                        <DataGridTextColumn Binding="{Binding [Comments]}" Header="Comments" Width="300" CanUserSort="False">
                        <DataGridTextColumn Binding="{Binding [SLA DATE]}" Header="SLA Date" Width="90" CanUserSort="False">

When user make any changes in db by editing a selected row of this datagrid, the datagrid has to be filled with recent datatable.

I am able to get correct datatable, but when it is given as Itemsource to datagrid, Its not showing recent one instead showing earlier one.

When I close the application and restart it, its showing correct one.

What I have tried:

I tried DataGrid.Items.Clear(); but am getting an error "Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead."

I tried DataGrid.Items.refresh(); and Datagrid.UpdateLayout(), but nothing are working.

Please let me know if there is a way to achieve it.

Thanks in advance