Question

在我当前的WPF应用程序中，需要在ViewModel中动态生成DataGrid的列。为此，我在System.Windows.Interactivity和行为中使用了该方法。因此，我完全按照这篇文章创建了ColumnsBehavior：

Is it possible to get dynamic columns on wpf datagrid in mvvm pattern?

当我初始化绑定列表并生成带有绑定的列时，一切工作正常。当我切换到ListBox以在每个ListBoxItem中显示一个DataGrid时，一切都再次正常运行。现在，我想在运行时将信息（模型）添加到边界列表中。选择ListBoxItem时，应显示相应的DataGrid。使用DataGrid上方的按钮，我可以将示例数据传递到边界列表对象。当我按下Button时，会生成正确数量的带有正确标题的列，但是该行仅在下一次出现时再次出现，其中ListBoxItem再次可见。这意味着数据是在刷新网格时出现的。

要将Botton Command属性绑定到ViewModel，我使用了ActionCommand实现：

RelayCommand

我正在使用MVVM模式。

这是我的 ViewModel ：

    public class ViewModel
    {
        public ViewModel()
        {
            ListItems = new ObservableCollection<ListItemModel>();
            ListItems.Add(new ListItemModel()
            {
                IsSelected = true
            });
            ListItems.Add(new ListItemModel()
            {
                IsSelected = false
            });

            FillCommand = new RelayCommand(FillAction);
        }

        public ObservableCollection<ListItemModel> ListItems { get; set; }

        public ListItemModel SelectedListItem { get; set; }

        public ICommand FillCommand { get; set; }

        public void FillAction(object sender)
        {
            SelectedListItem.Entries = new ObservableCollection<Entry>()
            {
                new Entry()
                {
                    Cells = new ObservableCollection<Cell>()
                    {
                        new Cell() { Cond1 = 11, Value = 99 },
                        new Cell() { Cond1 = 22, Value = 99 },
                        new Cell() { Cond1 = 33, Value = 99 }
                    }
                },
                new Entry()
                {
                    Cells = new ObservableCollection<Cell>()
                    {
                        new Cell() { Cond1 = 11, Value = 99 },
                        new Cell() { Cond1 = 22, Value = 99 },
                        new Cell() { Cond1 = 33, Value = 99 }
                    },
                },
                new Entry()
                {
                    Cells = new ObservableCollection<Cell>()
                    {
                        new Cell() { Cond1 = 11, Value = 99 },
                        new Cell() { Cond1 = 22, Value = 99 },
                        new Cell() { Cond1 = 33, Value = 99 }
                    },
                }
            };

            SelectedListItem.GenerateGrid();
        }
    }

用于保留列的属性在ListItemModel中。在下面的代码中可以看到DataGrid的ItemsSource背后的对象结构和columns属性：

public class ListItemModel
    {
        public ListItemModel()
        {
            Entries = new ObservableCollection<Entry>();
            DataColumns = new ObservableCollection<DataGridColumn>();
        }

        public ObservableCollection<Entry> Entries { get; set; }

        public ObservableCollection<DataGridColumn> DataColumns { get; set; }

        public bool IsSelected { get; set; }

        public void GenerateGrid()
        {
            if (Entries.Count != 0)
            {
                var columns = Entries[0]?.Cells;

                for (int i = 0; i < columns.Count; i++)
                {
                    Binding b = new Binding(string.Format("Cells[{0}].Value", i));
                    DataGridTextColumn text = new DataGridTextColumn();
                    text.Header = columns[i].Cond1.ToString();
                    text.Binding = b;
                    DataColumns.Add(text);
                }
            }
        }
    }

    public class Entry
    {
        public ObservableCollection<Cell> Cells { get; set; }

        public Entry() { Cells = new ObservableCollection<Cell>(); }
    }

    public class Cell
    {
        public Cell() { }

        public int Cond1 { get; set; }

        public int Value { get; set; }
    }
}

对于视图，您需要名称空间：

http://schemas.microsoft.com/expression/2010/interactivity

以下代码示例显示了视图。

<Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"></ColumnDefinition>
            <ColumnDefinition Width="*"></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <ListBox ItemsSource="{Binding ListItems}" SelectedItem="{Binding SelectedListItem}">
            <ListBox.Resources>
                <Style TargetType="{x:Type ListBoxItem}">
                    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
                </Style>
            </ListBox.Resources>
        </ListBox>
        <DockPanel Grid.Column="1">
            <Button DockPanel.Dock="Top" Command="{Binding FillCommand}">Fill Data</Button>
            <DataGrid x:Name="ToleranceGrid" ColumnWidth="*" ItemsSource="{Binding Path=SelectedListItem.Entries}"
                      CanUserAddRows="False" SelectionMode="Single" SelectionUnit="Cell" AutoGenerateColumns="False" local:ColumnsBindingBehaviour.BindableColumns="{Binding Path=SelectedListItem.DataColumns}">
            </DataGrid>
        </DockPanel>
    </Grid>

在后面的代码中，ViewModel设置为视图的DataContext。

结果应如下所示： WPF Application

选择第一个ListItemModel，然后按下DataGrid上方的Button。如您所见，列已生成，但未显示行。我调试了代码，在ViewModel中正确设置了所有内容。当我选择第二个ListItemModel并返回到第一个时，内容将正确显示。

您有什么想法吗？

Answer 1

当ListItemModel属性设置为新集合时，您的PropertyChanged应该实现INotifyPropertyChanged接口并引发Entries事件：

public class ListItemModel : INotifyPropertyChanged
{
    public ListItemModel()
    {
        Entries = new ObservableCollection<Entry>();
        DataColumns = new ObservableCollection<DataGridColumn>();
    }

    private ObservableCollection<Entry> _entries;
    public ObservableCollection<Entry> Entries
    {
        get { return _entries; }
        set { _entries = value; NotifyPropertyChanged(); }
    }

    public ObservableCollection<DataGridColumn> DataColumns { get; set; }

    public bool IsSelected { get; set; }

    public void GenerateGrid()
    {
        if (Entries.Count != 0)
        {
            var columns = Entries[0]?.Cells;

            for (int i = 0; i < columns.Count; i++)
            {
                Binding b = new Binding(string.Format("Cells[{0}].Value", i));
                DataGridTextColumn text = new DataGridTextColumn();
                text.Header = columns[i].Cond1.ToString();
                text.Binding = b;
                DataColumns.Add(text);
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propertyName = "")
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

动态生成列时如何解决DataGrid中行丢失的显示？

1 个答案: