How to delete a combobox's selected item from another Combobox

Question

I'm trying to create a simple ticket fair app but I'm stuck at some place. I have load-Data() method which populates the 2 combo box (destination & source), each contains the same list of cities. I want Destination's selected item(city) removed from the Source.

I disabled the source combo box which gets enabled from the Selection_Changed event of Destination combo box.

I tried removing selected item of Destination from source at Selection_Changed event. but then it occurred to me what if user selects wrong item in the first place? it will get removed from the source anyway.

Any advice how do I go about achieving this?

here's the code i tried:

private void DestinationCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
           // await LoadData();
        object selectedItem = DestinationCombo.SelectedItem;
            if(SourceCombo.Items.Contains(selectedItem))
            {
                SourceCombo.Items.Remove(selectedItem);
            }

        //await LoadData();
        SourceCombo.IsEnabled = true;
        }

'LoadDate' Method:

private async Task LoadData()
        {
            DestinationCombo.Items.Clear();
            SourceCombo.Items.Clear();
            file = await ApplicationData.Current.LocalFolder.GetFileAsync("jsonText.txt");
            var jsonContent = await FileIO.ReadTextAsync(file);

            DataModel2.RootObject states = JsonConvert.DeserializeObject<DataModel2.RootObject>(jsonContent);

            foreach (var state in states.country.state)
            {
                foreach (var city in state.city)
                {

                    DestinationCombo.Items.Add(city);
                    SourceCombo.Items.Add(city);

                }
            }
        }

Answer 1

First, where all these methods are, ie, in the class (most likely a Form#), declare a public variable called cities:-

public list<string> cities = new list<string>;

Then edit your loaddata() method a little:

private async Task LoadData()
    {
        DestinationCombo.Items.Clear();
        SourceCombo.Items.Clear();
        file = await ApplicationData.Current.LocalFolder.GetFileAsync("jsonText.txt");
        var jsonContent = await FileIO.ReadTextAsync(file);

        DataModel2.RootObject states = JsonConvert.DeserializeObject<DataModel2.RootObject>(jsonContent);

        foreach (var state in states.country.state)
        {
            foreach (var city in state.city)
            {
                cities.Add(city);
            }
        }

        DestinationCombo.Items.AddRange(cities.ToArray<String>());
        SourceCombo.Items.AddRange(cities.ToArray<String>());
    }

Finally, in the SourceCombo SelectionChanged Event , put this code:

private void SourceCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
       // await LoadData();
    object selectedItem = SourceCombo.SelectedItem;
    DestinationCombo.Items.Clear();
    DestinationCombo.Items.AddRange(cities.ToArray<String>());
    DestinationCombo.Items.Remove(selectedItem);
    }

You can also add similar code to the other ComboBox so that whichever ComboBox (Source or Destination) the user clicks, the selection is removed from the other ComboBox.