使用ViewModel绑定ComboBox源（mvvm wpf）

Question

this is my Code (my ViewModel:

                        NamesDB.Open();
                        string NamesCommand = "SELECT * FROM [Country]";
                        OleDbDataAdapter dr = new OleDbDataAdapter(new OleDbCommand(NamesCommand, NamesDB));
                        DataSet ds = new DataSet();
                        dr.Fill(ds);
                        var empList = ds.Tables[0].AsEnumerable().Select(dataRow => new Country { Name = dataRow.Field<string>("NameCountry")}).ToList();
                        Countries = empList;
                        NamesDB.Close();


    public List<Country> Countries { get; set; }

    public class Country
    {
        public string Name { get; set; }
    }

I am reading a whole Column from my DataBase and i am storing it in "empList". Atleast thats what i think im doing.

I have a Combobox and want to bind the Source to Countries in XAML:

 ItemsSource="{Binding Countries}"

but i dont get the names of the Countries and i dont know what im doing wrong

please help:(

thanks in advance

Answer 1

I think this is what you're trying to accomplish.

First your combobox should looks something like this.

<ComboBox DisplayMemberPath="Name" ItemsSource="{Binding Countries}"></ComboBox>

Model may look like this:

public class Country
{
    public string Name { get; set; }
}

Then your viewModel should look something like:

public class MainWindowViewModel : INotifyPropertyChanged
{

    public MainWindowViewModel()
    {
        GetData();
    }

    private List<Country> _countries;

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public List<Country> Countries
    {
        get => _countries;
        set
        {
            _countries = value;
            OnPropertyChanged();
        }

    }

    private void GetData()
    {
        // call database here
        var countries = new List<Country>()
        {
            new Country() {Name = "Usa"},
            new Country() {Name = "Mexico"},
        };

        Countries = countries;
    }
}public class MainWindowViewModel : INotifyPropertyChanged
{

    public MainWindowViewModel()
    {
        GetData();
    }

    private List<Country> _countries;

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public List<Country> Countries
    {
        get => _countries;
        set
        {
            _countries = value;
            OnPropertyChanged();
        }

    }

    private void GetData()
    {
        // call database here
        var countries = new List<Country>()
        {
            new Country() {Name = "Usa"},
            new Country() {Name = "Mexico"},
        };

        Countries = countries;
    }
}