Bind List<object> to Datagrid WPF, C#

Question

I'm totally new to WPF so heres my code:

 <DataGrid x:Name="dgVarConfig" ItemsSource="{Binding varConfigList, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Margin="10,59,0,0" VerticalAlignment="Top" Height="403" Width="1278" AutoGenerateColumns="False" CanUserAddRows="False" CanUserDeleteRows="False" CanUserResizeRows="False" HeadersVisibility="Column">

            <DataGrid.Columns>
                <DataGridTextColumn  Width="auto" Header="Match Ausdruck" Binding="{Binding match_expression}"></DataGridTextColumn>
            </DataGrid.Columns>
</DataGrid>

My Files: MainWindow.xaml, MainController.cs, VarConfigDAO.cs

the varConfigDAO.cs returns the list to the MainController, and the MainController.cs returns it do MainWindows.xaml.

This is the VarConfig.cs:

 public class VarConfig
    {
        public int id { get; set; }
        public String group { get; set; }
        public String machine { get; set; }
        public String match_expression { get; set; }
        public String variant_new_1 { get; set; }
        public String calc_formula_1 { get; set; }
        public String variant_new_2 { get; set; }
        public String calc_formula_2 { get; set; }
    }

It works if i set the itemssource programmaticly:

dgVarConfig.Itemssource = mainController.loadVarConfigList();

But thats not what i want because i want to update the list via the grid (insert, delete, update lines => Mode=TwoWay)

Any clue how i can fill the itemssource via xaml?

Answer 1

Create a view model class with a property that holds a collection of VarConfig objects. The collection should notify the view about changes (like added or removed elements). An appropriate collection type would therefore be ObservableCollection:

public class ViewModel
{
    public ObservableCollection<VarConfig> VarConfigList { get; }
        = new ObservableCollection<VarConfig>();
}

Set the DataContext of your UI (e.g. your MainWindow) to an instance of the view model, for example in code behind in the MainWindow constructor like this:

public MainWindow()
{
    InitializeComponent();

    var viewModel = new ViewModel();
    // fill viewModel.VarConfigList

    DataContext = viewModel;
}

Bind to the VarConfigList property in XAML. It is not necessary to set Mode=TwoWay or UpdateSourceTrigger=PropertyChanged, as the ItemsSource property is only bound one-way (the DataGrid - or any other ItemsControl - never sets it):

<DataGrid ItemsSource="{Binding VarConfigList}" ...>
    ...
</DataGrid>

Finally, if you also want the UI to react on changes of the individual VarConfig properties, it should implement the INotifyPropertyChanged interface:

public class VarConfig : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    private int id;
    public int Id
    {
        get { return id; }
        set
        {
            id = value;
            OnPropertyChanged(nameof(Id));
        }
    }

    // similar code for the other properties
}

Note the casing. It's widely accepted to write C# property names in PascalCase.