MVVM WPF：验证自动生成列的数据网格行

Question

我正在创建一个DataTable，其列存储在一个列表中。

public class CustomColumn
{
    public string ColumnName { get; set; }
    public int MinLength { get; set; }
    public int MaxLength { get; set; }
}

public class ViewModel
{
    public List<CustomColumn> Columns { get; set; }
    public DataTable MyTable { get; set; }

    public ViewModel()
    {
        InitializeCustomColumns();
        MyTable = new DataTable();

        foreach (CustomColumn column in Columns)
        {
            MyTable.Columns.Add(column.ColumnName, typeof(string));
        }
    }
}

现在我将DataTable 绑定到DataGrid 并允许用户在DataGrid 中添加行。我的DataGrid 列是在运行时初始化列列表时自动生成的。当用户在行的特定列中输入某个值时，我想根据CustomColumn Properties -> MinLength（最小字符串长度）和MaxLength（最大允许字符串长度）进行验证。如果验证失败，我想显示 DataGrid 中出现的默认红色边框以表示无效输入。我正在遵循 MVVM 软件架构模式。

编辑

我附上了ColumnChanging监听器

MyTable.ColumnChanging += tableColumnChanging;

private void tableColumnChanging(object sender, DataColumnChangeEventArgs e)
{
    //I am able to validate here using my logic
    if(!isValid(e))
    {
        object badValue = e.ProposedValue;
        e.ProposedValue = "Bad Data";
        e.Row.RowError = "The column contains an error";
        e.Row.SetColumnError(e.Column, "Column cannot be " + badValue);
    }
    else
    {
        ... 
    }

}

我能够验证，但我想用 ! 显示我的单元格标记isValid是否返回false。

Answer 1

我设法解决了同样的问题

xaml

<ScrollViewer xmlns:l="clr-namespace:CSharpWPF">
    <ScrollViewer.Resources>
        <DataTemplate DataType="{x:Type l:CustomTable}">
            <DataTemplate.Resources>
                <l:ErrorToVisibilityConverter x:Key="ErrorToVisibilityConverter" />
                <Style TargetType="DataGridCell">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="DataGridCell">
                                <Grid Background="{TemplateBinding Background}">
                                    <StackPanel Orientation="Horizontal">
                                        <TextBlock Text=" ! "
                                                   FontWeight="Bold"
                                                   Foreground="Red">
                                            <TextBlock.Visibility>
                                                <MultiBinding Converter="{StaticResource ErrorToVisibilityConverter}"
                                                              Mode="OneWay">
                                                    <Binding RelativeSource="{RelativeSource FindAncestor,AncestorType=DataGridCell}" />
                                                    <Binding Path="Tag.Errors"
                                                             RelativeSource="{RelativeSource FindAncestor,AncestorType=DataGrid}" />
                                                    <Binding />
                                                </MultiBinding>
                                            </TextBlock.Visibility>
                                        </TextBlock>
                                        <ContentPresenter />
                                    </StackPanel>
                                </Grid>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </DataTemplate.Resources>
            <StackPanel>
                ...
            </StackPanel>
        </DataTemplate>
    </ScrollViewer.Resources>
    <ContentControl Content="{Binding TableCollection}" />
</ScrollViewer>

我为DataGridCell 添加了Style，并使用我们的额外元素定义了一个自定义Template 以显示! 标记

转换器类

namespace CSharpWPF
{
    public class ErrorToVisibilityConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            DataGridColumn column = values[0] as DataGridColumn;
            ObservableCollection<DataColumnChangeEventArgs> errors = values[1] as ObservableCollection<DataColumnChangeEventArgs>;
            DataRowView view = values[2] as DataRowView;

            DataColumnChangeEventArgs args = errors.FirstOrDefault(e => (e.Row == view.Row) && (e.Column.Ordinal == column.DisplayIndex));

            return view.Row.HasErrors && args != null ? Visibility.Visible : Visibility.Collapsed;
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

这将检测当前单元格是否是受影响的单元格，如果为真则返回Visibility.Visible，否则返回Visibility.Collapsed，从而根据错误状态隐藏或显示额外元素

更改CustomTable

public CustomTable()
{
    ...

    Errors = new ObservableCollection<DataColumnChangeEventArgs>();
}

private void tableColumnChanging(object sender, DataColumnChangeEventArgs e)
{
    if (!isValid(e))
    {
        object badValue = e.ProposedValue;
        e.ProposedValue = "Bad Data";
        e.Row.RowError = "The column contains an error";
        e.Row.SetColumnError(e.Column, "Column cannot be " + badValue);
        Errors.Add(e);
        OnPropertyChanged("Errors");
    }
    else
    {
        DataColumnChangeEventArgs args = Errors.FirstOrDefault(ee => (ee.Row == e.Row) && (ee.Column == e.Column));
        if (args != null)
        {
            Errors.Remove(args);
            OnPropertyChanged("Errors");
        }
        //... 
    }
}

public ObservableCollection<DataColumnChangeEventArgs> Errors { get; set; }

结果

所以整个想法是添加一个具有通知更改功能的额外属性，并将其用作触发器和其他属性以检测适当的列，其余是我们额外的可见性！自定义模板中的元素