Troubleshooting Property Update Issues in WPF DataGridCheckBoxColumn Bindings

Why does the CheckBox state change in WPF DataGridCheckBoxColumn not automatically update the bound property?

Situation：

My code has correctly implemented the binding relationship using the MVVM library, but I am unable to filter data using the checkbox in the DataGrid.

//model
public class SpectralPeakDataItem
{
        public bool IsUserFor { get; set; }

        public double Wavelength { get; set; }

        public int PixelPosition { get; set; }

        public double InstensityPercentage { get; set; }
}

//ViewModel
[ObservableProperty]
private ObservableCollection<SpectralPeakDataItem> _mercuryArgonSpectralPeakDataItems = [];

<ui:DataGrid
    Grid.Column="0"
    Margin="5"
    AutoGenerateColumns="False"
    ItemsSource="{Binding MercuryArgonSpectralPeakDataItems, Mode=TwoWay}">
    <DataGrid.Columns>
        <DataGridCheckBoxColumn Binding="{Binding IsUserFor, Mode=TwoWay}" Header="IsUserFor" />
        <DataGridTextColumn Binding="{Binding Wavelength, Mode=TwoWay}" Header="Wavelength" />
        <DataGridTextColumn Binding="{Binding PixelPosition, Mode=TwoWay}" Header="PixelPosition" />
        <DataGridTextColumn Binding="{Binding InstensityPercentage, Mode=TwoWay}" Header="Percentage" />
    </DataGrid.Columns>
</ui:DataGrid>

However, in the usual event-driven code design, it works fine.So, I think this is an issue with MVVM’s data binding, as it doesn’t seem to achieve data synchronization.So next, I discovered that:In a WPF DataGridCheckBoxColumn, the reason why changes in the CheckBox’s checked state do not automatically trigger property updates is primarily because the DataGridCheckBoxColumn uses a binding context that may not directly reflect changes in the CheckBox state. This often involves the following issues:

1. Data Binding: The Binding property of DataGridCheckBoxColumn defaults to BindingMode.OneWay, which means it only updates data from the data source to the control, not from the control to the data source. Therefore, changes in the CheckBox state do not automatically update the property in the data source.

2. UpdateSourceTrigger: Even if the binding mode is set to TwoWay, if the UpdateSourceTrigger property is not configured correctly, it may result in the data source not being updated in a timely manner. By default, UpdateSourceTrigger may be set to LostFocus, meaning data will only update when the CheckBox loses focus.

3. ViewModel Implementation: If your ViewModel does not implement the INotifyPropertyChanged interface, or if the CheckBox state change does not trigger the appropriate notifications, data binding will not update correctly.

Solution:

• Set Binding Mode: Ensure that the DataGridCheckBoxColumn binding mode is set to TwoWay and the UpdateSourceTrigger is set to PropertyChanged. This will ensure that the data source is updated whenever the CheckBox state changes.

<DataGridCheckBoxColumn Header="Check" Binding="{Binding IsChecked, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

Then everything go well!