I'm facing some issues with my C# WPF project and, especially, the DataGridComboBoxColumn control. So, here's a part of my MainWindow.xaml file :

<DataGrid x:Name="WorkDayGrid"
          AutoGenerateColumns="False"
          CanUserAddRows="False"
          CanUserDeleteRows="False"
          CanUserSortColumns="False"
          ItemsSource="{Binding}">
    <DataGrid.Resources>
        <local:Times x:Key="times" />
        <local:TimeConverter x:Key="timeConverter" />
    </DataGrid.Resources>
    <DataGrid.Columns>
        <DataGridComboBoxColumn Header="Arrival Time"
                                ItemsSource="{StaticResource times}"
                                SelectedItemBinding="{Binding ArrivalTime, Converter={StaticResource timeConverter}}" />
    </DataGrid.Columns>
</DataGrid>

And the corresponding "code-behind" :

public partial class MainWindow : Window
{
    private ObservableCollection<WorkDay> _workDays = new ObservableCollection<WorkDay>();

    public MainWindow()
    {
        InitializeComponent();

        ComputeWorkDays();
        WorkDayGrid.DataContext = _workDays;
    }

    private void ComputeWorkDays()
    {
        _workDays.Clear();

        for (var i = 1; i <= 31;   i)
        {
            var d = new WorkDay();
            _workDays.Add(d);
        }
    }
}

The code of the WorkDay class :

class WorkDay
{
    public Time ArrivalTime { get; set; }
}

The code of the Times class :

class Times : ObservableCollection<Time>
{
    public Times()
    {
        var firstHour = 7;
        var lastHour = 20;
        var minuteStep = 5;

        for (var i = firstHour; i < lastHour;   i)
        {
            for (var j = 0; j < 60; j  = minuteStep)
            {
                var t = new Time
                {
                    Hour = i,
                    Minute = j
                };
                Add(t);
            }
        }
    }
}

The code of the Time class :

class Time
{
    private int _hour = 0;
    private int _minute = 0;

    public int Hour
    {
        set => _hour = value;
    }
    public int Minute
    {
        set => _minute = value;
    }

    public override string ToString()
    {
        var fmt = "D2";
        return _hour.ToString(fmt)   ":"   _minute.ToString(fmt);
    }
}

The code of the TimeConverter class :

class TimeConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value != null)
        {
            var time = (Time)value;
            return time.ToString();
        }
        else
        {
            string result = "";
            return result;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (Time)value;
    }
}

The problem is when I select a value in one cell (thanks to the related combo box), the same value is also displayed in another cell. In addition, when I scroll down to another row in the data grid, the selected value disappears. I wonder if the DataGridComboBoxColumn works well... I use the .NET framework 4.6.1. Thank you very much for your help.

CodePudding user response：

At the end of the day, it was the binding converter which caused the issue. Thank you @Clemens for your help.

FYI, I don't use the DateTime struct because I need an "invalid" time to allow the user to cancel its selection.