Question

我正在通过MultiBinding和IMultiValueConverter将属性更改检测集成到应用程序中。因此，当用户对“ DataGrid”进行更改时，DataGridCell' changes background color. My issue is that when the user saves their work I cannot remove the changed background without a screen flicker. I can do DataContext = null then DataContext = this`，但是会导致屏幕闪烁。我无法调用更新绑定将MultiBinding重置为默认值。

问：如何更新如下所示的DataGridCell上的MultiBinding？

很遗憾，这不是MVVM。我创建了一个显示问题的项目：https://github.com/jmooney5115/clear-multibinding

此解决方案适用于TextBox，但不适用于DataGridCell：

foreach (TextBox textBox in FindVisualChildren<TextBox>(this))
{
    multiBindingExpression = BindingOperations.GetMultiBindingExpression(textBox, TextBox.BackgroundProperty);
    multiBindingExpression.UpdateTarget();
}

这是数据网格单元格的多重绑定。多值转换器采用原始值和修改后的值。如果更改该值，则返回true，以将背景色设置为LightBlue。如果为false，则背景为默认颜色。

<DataGrid.Columns>
    <DataGridTextColumn Header="Destination Tag name" Binding="{Binding Path=Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
        <!-- https://stackoverflow.com/questions/5902351/issue-while-mixing-multibinding-converter-and-trigger-in-style -->
        <DataGridTextColumn.CellStyle>
            <Style TargetType="{x:Type DataGridCell}">
                <Style.Triggers>
                    <DataTrigger Value="True">
                        <DataTrigger.Binding>
                            <MultiBinding Converter="{StaticResource BackgroundColorConverterBool}">
                                <Binding Path="Name"    />
                                <Binding Path="Name" Mode="OneTime" />
                            </MultiBinding>
                        </DataTrigger.Binding>
                    </DataTrigger>

                    <Setter Property="Background" Value="LightBlue"></Setter>
                </Style.Triggers>
            </Style>
        </DataGridTextColumn.CellStyle>
    </DataGridTextColumn>
</DataGrid.Columns>

这是我正在使用的多值转换器：

/// <summary>
/// https://stackoverflow.com/questions/1224144/change-background-color-for-wpf-textbox-in-changed-state
/// 
/// Property changed and display it on a datagrid.
/// 
/// Boolean Converter
/// </summary>

public class BackgroundColorConverterBool : IMultiValueConverter
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="values"></param>
    /// <param name="targetType"></param>
    /// <param name="parameter"></param>
    /// <param name="culture"></param>
    /// <returns>True is property has changed</returns>
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values[0] is null || values[1] is null) return false;


        if (values.Length == 2)
            if (values[0].Equals(values[1]))
                return false;
            else
                return true;
        else
            return true;
    }

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

更新

使用标记为我的答案的解决方案，我可以对其进行扩展以推广UpdateState（）方法。

foreach (var prop in this.GetType().GetProperties())
    _memo[prop.Name] = prop.GetValue(this);

Answer 1

我不会依赖OneTime绑定模式和技巧来清除绑定来跟踪数据更改。改为实现类似Memento模式的内容。

添加此代码以将状态存储在Item类中：

private Dictionary<string, object> _memo = new Dictionary<string, object>();
public object this[string key]
{
    get 
    {
        object o;
        _memo.TryGetValue(key, out o);
        return o;
    }
}

public void UpdateState()
{
    _memo["Name"] = Name;
    _memo["Description"] = Description;
    _memo["Alias"] = Alias;
    _memo["Value"] = Value;
    OnPropertyChanged("Item[]");
}

要使索引器this[]工作，您必须重命名类（例如，重命名为ItemVm），因为类名和成员名不能相同，.NET使用"Item"作为索引器属性名称。

请注意，索引器的通知具有"Item[]"格式，并且VerifyProperty()方法也应固定：

private void VerifyProperty(string propertyName)
{
    if (propertyName == null || propertyName == "Item[]")
        return;

现在，要在窗口中使用未修改的值，请像这样绑定到索引器：

<Style TargetType="{x:Type DataGridCell}">
    <Style.Triggers>
        <DataTrigger Value="True">
            <DataTrigger.Binding>
                <MultiBinding Converter="{StaticResource BackgroundColorConverterBool}">
                    <Binding Path="Value"   />
                    <Binding Path="[Value]" />
                </MultiBinding>
            </DataTrigger.Binding>

            <Setter Property="Background" Value="LightBlue"/>
        </DataTrigger>
    </Style.Triggers>
</Style>

在创建项目时保存初始状态：

for(var i = 0; i < 100; i++)
{
    Items.Add(new ItemVm
    {
        Alias = string.Format("Item {0}", i.ToString()),
        Description = string.Format("Description {0}", i.ToString()),
        Name = string.Format("Name {0}", i.ToString()),
        Value = string.Format("Value {0}", i.ToString())
    });
    Items[i].UpdateState();
}

并单击按钮保存状态更改：

private void Button_Click(object sender, RoutedEventArgs e)
{
    UIHelper.UpdateDataBindings<Control>(this);

    foreach(var item in Items)
    {
        item.UpdateState();
    }
}

在DataGridCell上更新MultiBinding

1 个答案: