Set default value in WPF ComboBox

.net, c#, wpf

Solution

Here's a working sample:

Viewmodel:

 public MainWindow()
    {
        InitializeComponent();

        var vm = new ViewModel();
        this.DataContext = vm;
        this.Loaded += (o,e) => vm.LoadData();
    }

    public class ViewModel : INotifyPropertyChanged
    {
        private IList<Charges> taxList;
        public ICollectionView TaxList { get; private set; }

        public void LoadData()
        {                
            taxList = Charges.GetChargeList("taxes");

            TaxList = CollectionViewSource.GetDefaultView(taxList);
            RaisePropertyChanged("TaxList");

            TaxList.CurrentChanged += TaxList_CurrentChanged;              

            var noTax = taxList.FirstOrDefault(c => c.ChargeName == "No Tax");
            TaxList.MoveCurrentTo(noTax);
        }

        void TaxList_CurrentChanged(object sender, EventArgs e)
        {
            var currentCharge = TaxList.CurrentItem as Charges;
            if(currentCharge != null)
                MessageBox.Show(currentCharge.ChargeName);
        }



        public event PropertyChangedEventHandler PropertyChanged;
        public void RaisePropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

View:

<ComboBox x:Name="cboTaxList" 
              ItemsSource="{Binding TaxList}" 
              DisplayMemberPath="ChargeName"
              IsSynchronizedWithCurrentItem="True" />

Problem

I am using ComboBox ItemsSource property binding to display items from a List to combo box. Following is the code: ``` <ComboBox x:Name="Cmb_Tax" ItemsSource="{Binding TaxList}" DisplayMemberPath="ChargeName" SelectedItem="{Binding SelectedTax,UpdateSourceTrigger=PropertyChanged}" IsEditable="True" IsTextSearchEnabled="True" SelectionChanged="Cmb_Tax_SelectionChanged"/> Classes.Charges _selected_tax = new Classes.Charges(); public Classes.Charges SelectedTax { get { return _selected_tax; } set { _selected_tax = value; } } List<Classes.Charges> _taxlist = new List<Classes.Charges>(); public List<Classes.Charges> TaxList { get { return _taxlist; } set { _taxlist = value; OnPropertyChanged("TaxList"); } } ``` It displays the items in the combo box correctly. There is a particular item in TaxList `"No Tax"` which I want to be selected by default in the combo box. This item can be present at any index in the list (Not necessary first or last item of the list). I am trying to use the following code to set the selected index property of combo box, but sadly its not working. ``` TaxList = Classes.Charges.GetChargeList("Tax"); Cmb_Tax.DataContext = this; int i = TaxList.FindIndex(x => x.ChargeName == tax_name); Cmb_Tax.SelectedIndex = i; ``` The Method FindIndex() returns the index of the `"No Tax"` correctly but when I try assigning it to `SelectedIndex` of combo the `SelectedIndex` doesn't change. It stays at -1. Update1 ``` private void Cmb_Tax_SelectionChanged(object sender, SelectionChangedEventArgs e) { MessageBox.Show(SelectedTax.ChargeName); } ``` Update2 Updated the code as per suggested by @ElectricRouge ``` <ComboBox x:Name="Cmb_Tax" ItemsSource="{Binding TaxList, Mode=TwoWay}" DisplayMemberPath="ChargeName" SelectedItem="{Binding SelectedTax,UpdateSourceTrigger=PropertyChanged,Mode=TwoWay}" IsEditable="True" IsTextSearchEnabled="True" SelectionChanged="Cmb_Tax_SelectionChanged"/> Classes.Charges _selected_tax = new Classes.Charges(); public Classes.Charges SelectedTax { get { return _selected_tax; } set { _selected_tax = value; OnPropertyChanged("SelectedTax"); } } ObservableCollection<Classes.Charges> _taxlist = new ObservableCollection<Classes.Charges>(); public ObservableCollection<Classes.Charges> TaxList { get { return _taxlist; } set { _taxlist = value; OnPropertyChanged("TaxList"); } } public void Load_Tax(string tax_name = null, Classes.Charges selected_tax = null) { TaxList = Classes.Charges.GetParticularChargeList("Tax"); Cmb_Tax.DataContext = this; //Cmb_Tax.SelectedValue = tax_name; SelectedTax = selected_tax; //int i = TaxList.FindIndex(x => x.ChargeName == tax_name); //Cmb_Tax.SelectedIndex = i; } ``` Any idea why this must be happening? Also please suggest any other approach to display default in combo box.

Original source