IDataErrorInfo覆盖组合框错误样式

public class MyDataObject : IDataErrorInfo
{
    public string Error { get { return null; } }

    public string this[string columnName]
    {
        get
        {
            if (columnName == "PropertyName")
            {
                // 返回属性"PropertyName"的错误信息
                return "错误信息";
            }
            return null;
        }
    }
}

<ComboBox ItemsSource="{Binding MyDataObject}"
          SelectedItem="{Binding SelectedItem, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}">
    <Validation.ErrorTemplate>
        <ControlTemplate>
            <!-- 自定义的错误样式 -->
        </ControlTemplate>
    </Validation.ErrorTemplate>
</ComboBox>