如何在 WPF 和 MVVM 中对数据网格项进行分组？

Question

我在 WPF / .Net Framework 4.8 和 Prism for MVVM 上有一个应用程序。我不明白如何使用 MVVM 对数据网格中的项目进行分组。我发现的所有指南都仅在没有 MVVM 的情况下实现了此功能。使用 MVVM 找到的唯一一个对我不起作用（没有错误，但数据网格中也没有组）

主窗口有一个包含以下对象的数据网格：

Product p = new Product() {
    Id = "H196A",   //Any string
    Name = "Box A", //Any string
    Count = 3       //Any int
}

ViewModel 看起来像这样

public ObservableCollection<Product> MyCollection { get; set; }

public ViewModel()
{
    //Filling in the collection
}

并查看

<DataGrid ItemsSource="{Binding MyCollection}" AutoGenerateColumns="False">
    <DataGrid.Columns>
        <DataGridTextColumn Header="Id"/>
        <DataGridTextColumn Header="Name"/>
        <DataGridTextColumn Header="Count"/>
    </DataGrid.Columns>
</DataGrid>

我尝试通过这种方式将数据网格绑定到 CollectionViewSource：

public CollectionViewSource MyCollectionViewSource { get; set; }

public ViewModel()
{
    //Filling in the collection
    MyCollectionViewSource = new CollectionViewSource();
    MyCollectionViewSource.Source = MyCollection;
    MyCollectionViewSource.GroupDescriptions.Add(new PropertyGroupDescription(nameof(Product.Name)));
}

<DataGrid ItemsSource="{Binding MyCollectionViewSource.View}" AutoGenerateColumns="False">
    ...
</DataGrid>

但是没有成功

Answer 1

您可能会发现在 xaml 中将

CollectionViewSOurce

 定义为静态资源更容易。作为解释，

<Grid.Resources>

 只是一个字典，允许使用您定义的 

key

 引用静态对象，因此在本例中，键是 

GroupedProducts

。

<Window x:Class="data_grid_grouping.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:data_grid_grouping"
        mc:Ignorable="d"
        Background="Azure"
        Title="MainWindow" Width="500" Height="500" >
    <Window.DataContext>
        <local:ViewModel />
    </Window.DataContext>
    <Grid>
        <Grid.Resources>
            <CollectionViewSource x:Key="GroupedProducts" Source="{Binding MyCollection}">
                <CollectionViewSource.GroupDescriptions>
                    <PropertyGroupDescription PropertyName="Name"/>
                </CollectionViewSource.GroupDescriptions>
            </CollectionViewSource>
        </Grid.Resources>
        <DataGrid ItemsSource="{Binding Source={StaticResource GroupedProducts}}" AutoGenerateColumns="False" Margin="10, 5">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Name" Binding="{Binding Name}" Width="*" />
                <DataGridTextColumn Header="Count" Binding="{Binding Count}" />
                <DataGridTextColumn Header="Id" Binding="{Binding Id}" />
            </DataGrid.Columns>
            <DataGrid.GroupStyle>
                <GroupStyle>
                    <GroupStyle.HeaderTemplate>
                        <DataTemplate>
                            <TextBlock FontWeight="Bold" FontSize="14" Text="{Binding Name}" Margin="5" Foreground="Maroon"/>
                        </DataTemplate>
                    </GroupStyle.HeaderTemplate>
                </GroupStyle>
            </DataGrid.GroupStyle>
        </DataGrid>
    </Grid>
</Window>

---

使用 Prism.Mvvm 的最小可重现示例

public partial class MainWindow : Window
{
    public MainWindow() => InitializeComponent();
}
class ViewModel : BindableBase
{
    public ViewModel() 
    {
        var tmp = MyCollection.GroupBy(_=>_.Name);
        foreach (var tmpGroup in tmp)
        {
            var count = 1;
            foreach (Product product in tmpGroup)
            {
                product.Count = count++;
            }
        }
    }
    public ObservableCollection<Product> MyCollection { get; } = new ObservableCollection<Product>
    {
        new Product{ Name = "Hammer" },
        new Product{ Name = "Screwdriver Set" },
        new Product{ Name = "Drill Bit Set" },
        new Product{ Name = "Measuring Tape" },
        new Product{ Name = "Wrench" },
        new Product{ Name = "Drill Bit Set" },
        new Product{ Name = "Hammer" },
        new Product{ Name = "Wrench" },
        new Product{ Name = "Drill Bit Set" },
        new Product{ Name = "Hammer" },
        new Product{ Name = "Screwdriver Set" },
        new Product{ Name = "Measuring Tape" }
    };

    public event PropertyChangedEventHandler? PropertyChanged;
}
public class Product : BindableBase
{
    private int _count;
    public int Count
    {
        get => _count;
        set => SetProperty(ref _count, value);
    }

    private string _name = string.Empty;
    public string Name
    {
        get => _name;
        set => SetProperty(ref _name, value);
    }

    private string _id = Guid.NewGuid().ToString().ToLower().Replace("-", string.Empty);
    public string Id
    {
        get => _id;
        set => SetProperty(ref _id, value);
    }
}