用戶控件MVVM中的執行方法

Question

我正在開發我的第一個MVVM應用程序，並且無法使其正常工作。

在我的主窗口中，我有一個按鈕，它執行一個返回自定義數據表類型對象的SQL命令。

該窗口還包含一個用戶控件，該控件由一些列標題和一個托管DataGridView的窗體組成。 我需要以某種方式告訴用戶控件執行一個將數據傳遞給DataGridView的方法，以便它可以更新它的值。

我嘗試在我的WPF網格控件上創建一個依賴屬性，該屬性綁定到我的viewmodel的數據，但它沒有正確更新。

我怎樣才能讓它發揮作用？

- 編輯 -

這是我的LiteGrid用戶控件的XAML -

<UserControl x:Class="ReportUtility.Controls.LiteGrid.LiteGrid"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:wf="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
         xmlns:lite="clr-namespace:ReportUtility.Controls.LiteGrid"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300"
         DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="30"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <ScrollViewer x:Name="_scroll" VerticalScrollBarVisibility="Hidden" HorizontalScrollBarVisibility="Hidden">
        <ItemsControl ItemsSource="{Binding Columns}" Grid.Row="0" Background="AliceBlue">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate> 
                        <StackPanel Orientation="Horizontal"/>
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
        </ItemsControl>
    </ScrollViewer>
    <WindowsFormsHost Background="White" Grid.Row="1">
        <lite:LiteGridView x:Name="_liteGridView"/>
    </WindowsFormsHost>
</Grid>

我的主要觀點模型是：

public class MainWindowViewModel : DependencyObject
{
    private readonly ILiteTableSource _source;

    public ICommand ExecuteQueryCommand { get; set; }
    public LiteGridViewModel Grid { get; set; }
    public string SqlCommandText { get; set; }

    public MainWindowViewModel(ILiteTableSource source)
    {
        this.ExecuteQueryCommand = new ExecuteQueryCommand(this);

        _source = source;
        _source.DataArrived+=new Action<DataSources.LiteSource.LiteTable>(_source_DataArrived);
    }

    public void ExecuteQuery()
    {
        _source.Connection = new ServerConnection();
        _source.CommandText = this.SqlCommandText;
        _source.ExecuteQuery();
    }

    public LiteTable Results
    {
        get { return (LiteTable)GetValue(ResultsProperty); }
        set { SetValue(ResultsProperty, value); }
    }

    // Using a DependencyProperty as the backing store for Results.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ResultsProperty =
        DependencyProperty.Register("Results", typeof(LiteTable), typeof(MainWindowViewModel), new UIPropertyMetadata(null));

    void _source_DataArrived(LiteTable data)
    {

        this.Results = data;
    }
}

和XAML：

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="50"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Button Grid.Row="0" Content="TestButton" HorizontalAlignment="Stretch" Command="{Binding ExecuteQueryCommand}"/>
    <TextBox Grid.Row="1" Text="{Binding Path=SqlCommandText, UpdateSourceTrigger=PropertyChanged}"/>
    <lite:LiteGrid Grid.Row="2" Data="{Binding Data, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>

Answer 1

既然你有一個LiteGridViewModel與你的LiteGrid一起使用，為什么不直接從ViewModel執行命令？

使用您問題中發布的代碼，我會：

這增加了資源，以確保LiteGridViewModel使用繪制LiteView

<Window.Resources> <!-- Or Grid.Resources if you prefer -->
    <DataTemplate DataType="{x:Type lite:LiteGridViewModel}">
        <lite:LiteGrid />
    </DataTemplate>
</Window.Resources>

用ContentControl替換MainView的<lite:LiteGrid ... />控件以顯示ViewModel

<ContentControl Content="{Binding Grid}" />

刪除MainViewModel上的Data屬性，因為它應該存儲在LiteGridViewModel ，而不是MainViewModel

在您的MainWindowViewModel使用LiteGridViewModel而不是嘗試通過View使用ViewModel

Grid = new LiteGridViewModel();

void _source_DataArrived(LiteTable data)
{
    Grid.Data = data;  // Fill property in ViewModel
    Grid.UpdateData(); // Call command on ViewModel
}

Answer 2

public LiteTable Data
{
    get { return (LiteTable)GetValue(DataProperty); }
    set 
    {
        object oldvalue = Data;
        SetValue(DataProperty, value);
        OnPropertyChanged(new DependencyPropertyChangedEventArgs(DataProperty, oldvalue, value));
    }
}

// Using a DependencyProperty as the backing store for Data.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty DataProperty =
    DependencyProperty.Register("Data", typeof(LiteTable), typeof(LiteGrid), new UIPropertyMetadata(null));

試試這個...