Syncfusion SfDataGrid基于值改单元格前景色异常排查

尝试通过转换器根据ItemsSource中对象的DateTime值修改Syncfusion SfDataGrid单元格的前景色，但运行程序时抛出异常：'GridCell' TargetType与元素'GridCell'类型不匹配，该异常逻辑矛盾，请求排查问题。

相关代码 #

数据模型（ItemsSource来源） #

public class RelationalTable 
{
    public int ClaimNumber { get; set; }
    public DateTime PlanPosted { get; set; }
    public DateTime PlanDue { get; set; }
    public int PlanVersion { get; set; }
    public string Department { get; set; }
}

SfDataGrid XAML标记 #

<UserControl.Resources>
<!-- converter is defined in the UserControl header xmlns:converter=<assembly holding the converter code> -->
    <converter:StyleConverterByDate x:Key="ConverterResult" />
</UserControl.Resources>

<sf:SfDataGrid x:Name="SfGrid" ItemsSource="{Binding ClaimList}" AutoGenerateColumns="False"
               IsReadOnly="True" AllowSorting="True" AllowFiltering="True"
               FontFamily="{StaticResource AppFont}"
               AllowEditing="False" AllowTriStateSorting="True" ColumnSizer="AutoWithLastColumnFill"
               RowHeight="32">

    <i:Interaction.Behaviors>
        <loc:SfDataGridBehavior />
    </i:Interaction.Behaviors>
    <sf:SfDataGrid.Columns>
        <sf:GridTextColumn HeaderText="Claim Number"
                           HorizontalHeaderContentAlignment="Left"
                           MappingName="ClaimNumber">
        </sf:GridTextColumn>
        <sf:GridDateTimeColumn CustomPattern="MM/dd/yyyy"
                               HorizontalHeaderContentAlignment="Left"
                               HeaderText="Date Posted"
                               MappingName="PlanPosted"
                               Pattern="CustomPattern" />
        <sf:GridDateTimeColumn CustomPattern="MM/dd/yyyy"
                               HorizontalHeaderContentAlignment="Left"
                               HeaderText="Date Due"
                               MappingName="PlanDue"
                               Pattern="CustomPattern">

            <sf:GridDateTimeColumn.CellStyle>
                <Style TargetType="sf:GridCell">
                    <Setter Property="Foreground" Value="{Binding PlanDue, Converter={StaticResource ConverterResult}}" />
                </Style>
            </sf:GridDateTimeColumn.CellStyle>

        </sf:GridDateTimeColumn>
            
        <sf:GridTextColumn HeaderText="Department"
                           HorizontalHeaderContentAlignment="Left"
                           MappingName="Department" />

    </sf:SfDataGrid.Columns>
</sf:SfDataGrid>

转换器代码 #

public class StyleConverterByDate : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        DateTime _value = (DateTime)value;
        DateTime _today = DateTime.Today;

        if (_value.Date >= _today.Date)
            return new SolidColorBrush(Colors.Red);
  
        if (_value.Date > _today.Date.AddDays(-10) && _value.Date < _today.Date)
            return new SolidColorBrush(Colors.Yellow);

        return new SolidColorBrush(Colors.Black);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return new SolidColorBrush(Colors.Black);
    }
}

这个异常看似矛盾，实际是命名空间冲突或Style定义方式错误导致的，以下是具体修复步骤：

1. 确认GridCell命名空间一致性 #

检查XAML头部的xmlns:sf命名空间是否指向正确的Syncfusion程序集（通常为xmlns:sf="clr-namespace:Syncfusion.UI.Xaml.Grid;assembly=Syncfusion.SfGrid.WPF"），避免项目中存在自定义GridCell类或其他程序集同名类造成混淆。

2. 修改CellStyle定义方式 #

针对Syncfusion的GridDateTimeColumn，直接设置CellStyle时需确保样式继承默认单元格样式：

<sf:GridDateTimeColumn.CellStyle>
    <Style TargetType="sf:GridCell" BasedOn="{StaticResource {x:Type sf:GridCell}}">
        <Setter Property="Foreground" Value="{Binding PlanDue, Converter={StaticResource ConverterResult}}" />
    </Style>
</sf:GridDateTimeColumn.CellStyle>

如果上述方法无效，可改用CellTemplate替代CellStyle，彻底规避样式冲突：

<sf:GridDateTimeColumn CustomPattern="MM/dd/yyyy"
                       HorizontalHeaderContentAlignment="Left"
                       HeaderText="Date Due"
                       MappingName="PlanDue"
                       Pattern="CustomPattern">
    <sf:GridDateTimeColumn.CellTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding PlanDue, StringFormat='MM/dd/yyyy'}"
                       Foreground="{Binding PlanDue, Converter={StaticResource ConverterResult}}"
                       VerticalAlignment="Center" />
        </DataTemplate>
    </sf:GridDateTimeColumn.CellTemplate>
</sf:GridDateTimeColumn>

3. 优化转换器健壮性 #

虽然不是异常直接原因，建议在转换器中添加空值判断避免潜在崩溃：

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    if (value is not DateTime dateValue)
        return new SolidColorBrush(Colors.Black);
        
    DateTime today = DateTime.Today;

    if (dateValue.Date >= today.Date)
        return new SolidColorBrush(Colors.Red);
  
    if (dateValue.Date > today.AddDays(-10) && dateValue.Date < today.Date)
        return new SolidColorBrush(Colors.Yellow);

    return new SolidColorBrush(Colors.Black);
}

内容的提问来源于stack exchange，提问作者Tim Jones