How Can I save a ComboBox selected value in settings file when it has dynamic content in WPF?

Question

I have a WPF application where I use many ComboBox controls. Most of the time I save application user settings in the Settings file, though many people use JSON to do that work but I think the default Settings file in WPF application is provided by Microsoft is far more better to use and robust also.

Now come in to the main topic, suppose if I want to save the Combobox last selected value before my application is closed then I just create a user settings and give the type "string" and declare it in the window closing event.

Here is the example, suppose I create a user settings name "ComboBoxStateThree" and give the type "string".

so, the code will be

Properties.Settings.Default.ComboBoxStateThree = cmb1.SelectedValue.ToString();

and if I want to do through pure XAML then the code of the Binding is

SelectedValuePath="Content" SelectedValue="{Binding Source={x:Static p:Settings.Default}, Path=ComboBoxStateThree, Mode=TwoWay}"

Both methods works great but the XAML approach is too much fast. And another important point is, I save the user Settings file in a separate folder name Properties.

I can save any ComboBox value by those method. But theres a catch. This method only works when the Combobox have predefined static values but if the Combobox itemsource bind to ObservableCollection or any listcollection view (List<>) then it is not working anymore.

One of my Combobox itemsource binded to a List and a added the itemsource from code behind.

Here is some code snippet.

 Marshal.ReleaseComObject(pDeviceCollection);
                ListCollectionView lcv = new(devices);
 lcv.GroupDescriptions.Add(new PropertyGroupDescription("Direction"));
 cmb1.ItemsSource = lcv;

my Combobox name is cmb1 in this case.

My question is, How Can I save the cmb1 selected value in settings file because in this case the ItemSource is the List and the List has different values depending upon situation, in a single sentence the CoboBox has dynamic content.

Answer 1

I try to reproduce the problem environment and rewrite the OnClosing method. It can work. You could check it out.

Here's saving the SelectedItem to a setting file.

<Window x:Class="SelectedItemSave.MainWindow"
       ...
        xmlns:local="clr-namespace:SelectedItemSave"
         xmlns:p="clr-namespace:SelectedItemSave.Properties"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <StackPanel>
            <Button x:Name="btn" Click="btn_Click" Height="30" Content=" add item"/>
            <ComboBox Name="cmb1" Height="50" ItemsSource="{Binding Icv}"  DisplayMemberPath="Name"   
                  SelectedValue="{Binding Source={x:Static p:Settings.Default}, Path=p, Mode=TwoWay}" SelectedValuePath="Id"/>
        </StackPanel>
    </Grid>
</Window>

Codebehind:

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;
using System.Windows.Data;

namespace ComboBoxSaveSelectedItem
{
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public int flag = 2;
        public MainWindow()
        {

            InitializeComponent();
            DataContext = this;
            if (flag != null)
            {
                string sIdDefaultRender = null;

                devices.Add(new AudioDevice() { Name = "System default", Direction = "Playback", Id = sIdDefaultRender, Default = true });

                devices.Insert(devices.Count - 0, new AudioDevice() { Name = "Selected application ...", Direction = "Recording", Id = "Idlast", Default = false });

                Icv = new ListCollectionView(devices);
                Icv.GroupDescriptions.Add(new PropertyGroupDescription("Direction"));

                this.cmb1.ItemsSource = Icv;
            }
            DataContext = this;
        }
        private ObservableCollection<AudioDevice> devices = new ObservableCollection<AudioDevice>();
        public ObservableCollection<AudioDevice> Devices
        {
            get { return devices; }
            set
            {
                if (devices != value)
                {
                    devices = value;
                    OnPropertyChanged("Devices");
                }
            }
        }
        private AudioDevice selectedItem;

        public AudioDevice SelectedItem
        {
            get { return selectedItem; }
            set
            {
                selectedItem = value;
                OnPropertyChanged("SelectedItem");
            }
        }
        private ICollectionView icv;

        public ICollectionView Icv
        {
            get { return icv; }
            set
            {
                icv = value;
                OnPropertyChanged("Icv");
            }
        }
       
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged([CallerMemberName] string name = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }

        protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
        {
            Properties.Settings.Default.Save();
            base.OnClosing(e);
        }


    }
    public class AudioDevice
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public string Direction { get; set; }
        public bool Default { get; set; }
        public AudioDevice() { }
    }
}

The result:

-

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