WPF Combobox selection changed not reflected correctly to datagrid

Question

I have a Combobox that has a dropdown list of different versions. And when I clicked one of the values in the Combobox, it supposes to show the responding data for this specific version. But when I run the code, the first click (let's said 2019) on Combobox value is not doing anything. If I click the other one (2020), it shows the data related to 2019. DataGrid seems always one click later than Combobox selection.

Here is my code:

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            dropdownList.Items.Add("<all>");
            dropdownList.SelectedIndex = 0;
            grid_Construct();
        }
        private void grid_Construct()
        {
            dataGrid1.Items.Clear();

            .......

            foreach (string file in files)
            {
                .........

                if (version == dropdownList.Text || dropdownList.Text == "<all>")
                {
                    dataGrid1.Items.Add(new pluginItem { addinversion = version, filepath = file });
                }
                if (!dropdownList.Items.Contains(version))
                {
                    dropdownList.Items.Add(version);
                }
            }
        }

        private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            grid_Construct();
        }

        public class pluginItem
        {
            public string addinversion { get; set; }
            public string filepath { get; set; }
        }
    }

XAML:

<Grid Grid.ColumnSpan="2" Height="34" VerticalAlignment="Top" Background="#FF9C9B9B">
            <Button x:Name="btnAbout" Content="About" Margin="0,6,24,7" Click="BnAbout_Click" RenderTransformOrigin="1.229,0.459" HorizontalAlignment="Right" Width="58"/>
            <Label Content="Revit Version : " HorizontalAlignment="Left" Height="27" Margin="12,2,0,0" VerticalAlignment="Top" Width="140"/>
            <ComboBox x:Name="dropdownList" HorizontalAlignment="Left" Height="21" Margin="101,6,0,0" 
                      VerticalAlignment="Top" Width="178" SelectionChanged="ComboBox_SelectionChanged" SelectedIndex="0"
                      ItemsSource="{Binding Path=pluginItem}"/>
        </Grid>
        <DataGrid x:Name="dataGrid1" Grid.ColumnSpan="2" Margin="15,54,15,51" Background="White" 
                  HeadersVisibility="Column" MinColumnWidth="5" RowHeight="22" CanUserReorderColumns="False" 
                  AreRowDetailsFrozen="True" RowDetailsVisibilityMode="Visible" CanUserAddRows="False" 
                  SelectionChanged="dataGrid1_SelectionChanged" ItemsSource="{Binding Path=pluginItem}" VirtualizingStackPanel.IsVirtualizing="False">

            <DataGrid.Columns>
                <DataGridTextColumn Header="Version" Width="118*" Binding="{Binding addinversion}" IsReadOnly="True"/>
                <DataGridTextColumn Header="Addin Path" Width="440*" Binding="{Binding filepath}" IsReadOnly="True"/>
            </DataGrid.Columns>

Answer 1

This is because you call grid_Construct(); in ComboBox_SelectionChanged(..) and at this point the change is not applied yet(at least by the ComboBox.Text), so the ComboBox.Text returns the old value.

Correction would be

if (version == (dropdownList.SelectedValue as string) || (dropdownList.SelectedValue as string) == "<all>")