大量意外 "Cannot retrieve value using the binding" 错误

Question

调试我的 wpf 项目时，我看到输出 window 中记录了很多绑定错误，例如：

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=AreRowDetailsFrozen; DataItem=null; target element is 'DataGridDetailsPresenter' (Name=''); target property is 'SelectiveScrollingOrientation' (type 'SelectiveScrollingOrientation')

我在谷歌上搜索了很多关于此类消息的信息，并尝试修复所有 my 绑定，但是对于我从未听说过的属性，错误不断发生。

所以我将其分解为一个基本示例：

xaml:

<StackPanel>
    <DataGrid ItemsSource="{Binding Items}" x:Name="_grid" CanUserAddRows="False">
        <DataGrid.Columns>
            <DataGridTextColumn Header="ID" Binding="{Binding ID, FallbackValue=0}"/>
            <DataGridTextColumn Header="Text" Binding="{Binding Text, FallbackValue={x:Null}}"/>
        </DataGrid.Columns>
    </DataGrid>
    <Button Click="Button_OnClick">Reset</Button>
</StackPanel>

后面的代码：

public partial class MainWindow
{
    public ObservableCollection<TestItem> Items { get; } = new ObservableCollection<TestItem>();    
    public MainWindow()
    {
        Items.Add(new TestItem { ID = 1, Text = "One" });
        Items.Add(new TestItem { ID = 2, Text = "Two" });
        InitializeComponent();
    }
    private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
    {
        _grid.ItemsSource = null;
        _grid.ItemsSource = Items;
    }
}

public class TestItem
{
    public int ID { get; set; }
    public string Text { get; set; }
}

两个元素在DataGrid中正确显示。

现在，每当我单击按钮（并重新分配 ItemSource）时，我都会在输出中看到这 12 条消息 window:

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=AreRowDetailsFrozen; DataItem=null; target element is 'DataGridDetailsPresenter' (Name=''); target property is 'SelectiveScrollingOrientation' (type 'SelectiveScrollingOrientation')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=HeadersVisibility; DataItem=null; target element is 'DataGridRowHeader' (Name=''); target property is 'Visibility' (type 'Visibility')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=ID; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=Text; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=ValidationErrorTemplate; DataItem=null; target element is 'Control' (Name=''); target property is 'Template' (type 'ControlTemplate')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=(0); DataItem=null; target element is 'Control' (Name=''); target property is 'Visibility' (type 'Visibility')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=AreRowDetailsFrozen; DataItem=null; target element is 'DataGridDetailsPresenter' (Name=''); target property is 'SelectiveScrollingOrientation' (type 'SelectiveScrollingOrientation')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=HeadersVisibility; DataItem=null; target element is 'DataGridRowHeader' (Name=''); target property is 'Visibility' (type 'Visibility')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=ID; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=Text; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=ValidationErrorTemplate; DataItem=null; target element is 'Control' (Name=''); target property is 'Template' (type 'ControlTemplate')
System.Windows.Data Information: 10 : Cannot retrieve value using the binding and no valid fallback value exists; using default instead. BindingExpression:Path=(0); DataItem=null; target element is 'Control' (Name=''); target property is 'Visibility' (type 'Visibility')

我检查了将 ItemSource 设置回 Items 时出现的错误，而不是设置为 null 时出现的错误。并且错误消息的数量取决于集合中的项目数量。

我担心这些 "binding errors" 会减慢我的实际应用程序（我的集合中可能有 >50k 元素），因此 想了解它们出现的原因以及我如何能够避开它们.

如您所见，我已经为我的绑定添加了回退值，但是对于我根本没有绑定的属性，错误不断出现。

Answer 1

这些绑定错误是无害的，除了修改构成 DataGrid 的元素的默认模板之外，您无能为力地消除它们，这不仅需要相当大的努力，而且它还可能会失去控件的某些内置功能。

你显然应该避免你自己负责的绑定错误，但是当涉及到你从框架 "inherit" 没有自定义任何模板的绑定错误时，你可以安全地忽略它们。大多数这些绑定错误都是无害的，并且已经在内部进行了处理。因此，只需忽略它们，什么也不做或压制它们。详情请参考以下link

解决 WPF 中无害的绑定错误： https://weblogs.asp.net/akjoshi/resolving-un-harmful-binding-errors-in-wpf

大量意外 "Cannot retrieve value using the binding" 错误

Lots of unexpected "Cannot retrieve value using the binding" errors

data-binding

wpf

datagrid

wpfdatagrid