绑定到模板中的整个对象时如何强制刷新绑定

Question

我有一个“规则”类列表，它是 DataGrid 的来源。在此示例中，我有一列是绑定到“已验证”依赖项属性的 DataGridTemplateColumn。

我遇到的问题是我有一个 VerifyColorConverter，我希望在其中传递所选行的整个“规则”对象，以便检查规则实例并返回适当的画笔。我在设置边框的背景时这样做（参见下面的代码 - Background="{Binding Converter={StaticResource convVerify}}"）

<DataGridTemplateColumn Header="Verified" Width="150">
<DataGridTemplateColumn.CellTemplate>
    <DataTemplate>
        <Border Background="{Binding Converter={StaticResource convVerify}}" 
                CornerRadius="4" Height="17" Margin="2,0,2,0" VerticalAlignment="Center" >
            <Grid>
                <TextBlock Foreground="Yellow" Text="{Binding Path=Verified, Mode=OneWay}" TextAlignment="Center" VerticalAlignment="Center" 
                        FontSize="11" FontWeight="Bold" />
            </Grid>
        </Border>
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>

当我在 DataGrid 上设置源时，这一切都很好，但是当底层的“规则”对象被改变时，转换器不会被调用，所以画笔保持不变。当我更改“规则”实例的某些属性时，如何强制更新它？

任何帮助表示赞赏！

转换器大致如下：

    [ValueConversion(typeof(CRule), typeof(SolidColorBrush))]
public class VerifyColorConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType,
        object parameter, System.Globalization.CultureInfo culture)
    {
        CRule rule = value as CRule;

        Color clr = Colors.Red;

        int count = 0;
        int verified = 0;

        if (rule != null)
        {
            count = rule.TotalCount;    
            verified = rule.NoOfVerified; 
        }

        if (count == 0) clr = Colors.Transparent;
        else if (verified == 0) clr = (Color)ColorConverter.ConvertFromString("#FFD12626");
        else if (verified < count) clr = (Color)ColorConverter.ConvertFromString("#FF905132");
        else clr = (Color)ColorConverter.ConvertFromString("#FF568D3F");

        SolidColorBrush brush = new SolidColorBrush(clr);
        return brush;
    }

    public object ConvertBack(object value, Type targetType,
        object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    #endregion
}

编辑

这是 Rule 类的一部分：

   /// <summary>
/// Compliance Restriction (Rule)
/// </summary>
public class Rule : BindElement
{
    public CMode Mode { get; private set; }
    public int RuleID { get; private set; }
    public string RuleDescription { get; private set; }

    private int _NoOfVerified = 0;
    private int _TotalCount = 0;

    public int NoOfVerified
    {
        get { return _NoOfVerified; }
        set { _NoOfVerified = value; RaiseChanged("Progress"); RaiseChanged("Verified"); }
    }

    public int TotalCount
    {
        get { return _TotalCount; }
        set { _TotalCount = value; RaiseChanged("Progress"); RaiseChanged("Verified"); }
    }

    public string Verified 
    {
        get 
        {
            if (TotalCount == 0) return "Nothing to verify";
            return string.Format("Verified {0} out of {1}", NoOfVerified, TotalCount); 
        }
    }

Answer 1

您可以尝试使用MultiValueConverter 而不是常规的Converter，并将您需要的任何规则属性传递给它，或者您可以在规则上的属性发生更改时引发CollectionChanged 事件。我通常不喜欢这样做，因为我不知道这会如何影响性能，但这是一种选择。

使用多转换器

public object Convert(object[] values, Type targetType,
    object parameter, System.Globalization.CultureInfo culture)
{
    Color clr = Colors.Red;

    int count = 0;
    int verified = 0;

    if (values.Count >= 2
        && int.TryParse(count, values[0].ToString()) 
        && int.TryParse(verfieid, values[1].ToString()))
    {
        if (count == 0) clr = Colors.Transparent;
        else if (verified == 0) clr = (Color)ColorConverter.ConvertFromString("#FFD12626");
        else if (verified < count) clr = (Color)ColorConverter.ConvertFromString("#FF905132");
        else clr = (Color)ColorConverter.ConvertFromString("#FF568D3F");
    }

    SolidColorBrush brush = new SolidColorBrush(clr);
    return brush;
}

用于 MultiConverter 的 XAML：

<Border.Background>
    <MultiBinding Converter="{StaticResource convVerify}">
        <Binding Value="{Binding TotalCount}" />
        <Binding Value="{Binding NoOfVerified}" />
    </MultiBinding>
</Border.Background>

使用属性更改事件

RulesCollection.CollectionChanged += RulesCollection_Changed;

void RulesCollection_Changed(object sender, CollectionChangedEventArgs e)
{
    if (e.NewItems != null)
        foreach(Rule rule in e.NewItems) // May need a cast here
            rule.PropertyChanged += Rule_PropertyChanged;

    if (e.OldItems != null)
        foreach(Rule rule in e.OldItems) // May need a cast here
            rule.PropertyChanged -= Rule_PropertyChanged;
}

void Rule_PropertyChanged()
{
    RaisePropertyChanged("RulesCollection");
}

Answer 2

好的 - 我找到了解决这个问题的方法 - 我所做的是将对象公开为属性，然后在任何更改时为此属性调用 OnPropertyChanged。这会被 Bind 对象正确拾取，并在属性更改时移交给 Converter！

    [Serializable()]
public class BindElement : INotifyPropertyChanged
{
    #region INotifyPropertyChanged Members

    [field: NonSerialized]
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, e);
    }

    public void RaiseChanged(string s)
    {
        OnPropertyChanged(new PropertyChangedEventArgs(s));
    }

    #endregion
}

public class BindElement2 : BindElement
{
    public void RaiseChanged(string s)
    {
        base.RaiseChanged(s);
        NudgeMyself();
    }

    public void NudgeMyself()
    {
        base.RaiseChanged("Myself");
    }
}

   /// <summary>
/// Compliance Restriction (Rule)
/// </summary>
public class CRule : BindElement2
{
    public CMode Mode { get; private set; }
    public int RuleID { get; private set; }
    public string RuleDescription { get; private set; }

    private int _NoOfVerified = 0;
    private int _TotalCount = 0;

    public int NoOfVerified
    {
        get { return _NoOfVerified; }
        set { _NoOfVerified = value; RaiseChanged("Progress"); RaiseChanged("Verified"); }
    }

    public int TotalCount
    {
        get { return _TotalCount; }
        set { _TotalCount = value; RaiseChanged("Progress"); RaiseChanged("Verified"); }
    }

    public string Verified 
    {
        get 
        {
            if (TotalCount == 0) return "Nothing to verify";
            return string.Format("Verified {0} out of {1}", NoOfVerified, TotalCount); 
        }
    }

    public CRule Myself
    {
        get { return this; }
    }

其他类可以从 BindElement2 派生并做同样的事情：（创建一个属性 Myself 来公开实例本身）

    public class CTradeRule : BindElement2
{
    public CRule Rule { get; set; }
    public bool IsLocked { get; set; }      // if true this should prevent a Reason from being given
    public bool IsVerified { get { return Reason.Length > 0; } }

    private string _Reason = "";        // ** no reason **
    public string Reason 
    {
        get { return _Reason; }
        set { _Reason = value; RaiseChanged("Reason"); }
    }

    public int Progress
    {
        get { return (IsVerified ? 1 : 0); }
    }

    public override string ToString()
    {
        return string.Format("Rule: {0}, Reason: {1}", Rule.RuleID, _Reason);
    }

    public CTradeRule Myself
    {
        get { return this; }
    }
}

现在在 xaml 中我可以这样做：（注意 Binding Path=Myself）然后确保在任何属性更改时将整个对象发送到转换器！

<DataGridTemplateColumn Header="Verified" Width="150">
<DataGridTemplateColumn.CellTemplate>
    <DataTemplate>
        <Border Background="{Binding Path=Myself, Converter={StaticResource convVerify}}" 
                CornerRadius="4" Height="17" Margin="2,0,2,0" VerticalAlignment="Center" >
            <Grid>
                <TextBlock Foreground="Yellow" Text="{Binding Path=Verified, Mode=OneWay}" TextAlignment="Center" VerticalAlignment="Center" 
                        FontSize="11" FontWeight="Bold" />
            </Grid>
        </Border>
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>