目前无法绑定到任何内容,这是正确的吗?Nullable<T>
在通用 XAML 应用程序中?
我找到了 2013 年的这个链接:
https://social.msdn.microsoft.com/Forums/en-US/befb9603-b8d6-468d-ad36-ef82a9e29749/textbox-text-binding-on-nullable-types?forum=winappswithcsharp https://social.msdn.microsoft.com/Forums/en-US/befb9603-b8d6-468d-ad36-ef82a9e29749/textbox-text-binding-on-nullable-types?forum=winappswithcsharp
说明:
Windows 8 应用商店应用程序不支持绑定到可为 null 的值。它只是没有进入这个版本。我们已经发现了 v.Next 的此行为错误。
但这真的是还没有解决吗?
我的绑定:
<TextBox Text="{Binding Serves, Mode=TwoWay}" Header="Serves"/>
我的财产:
public int? Serves
{
get { return _serves; ; }
set
{
_serves = value;
OnPropertyChanged();
}
}
我的输出中出现错误:
Error: Cannot save value from target back to source.
BindingExpression:
Path='Serves'
DataItem='MyAssembly.MyNamespace.RecipeViewModel, MyAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'; target element is 'Windows.UI.Xaml.Controls.TextBox' (Name='null'); target property is 'Text' (type 'String').
好像没固定啊由于 XAML 使用内置转换器,在这种情况下,您可以将其与您自己的转换器交换,处理可空值:
XAML:
<StackPanel Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<StackPanel.Resources>
<local:NullConverter x:Key="NullableIntConverter"/>
</StackPanel.Resources>
<TextBox Text="{Binding Serves, Mode=TwoWay, Converter={StaticResource NullableIntConverter}}" Header="Serves"/>
</StackPanel>
背后代码:
public class NullConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, string language)
{ return value; }
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
int temp;
if (string.IsNullOrEmpty((string)value) || !int.TryParse((string)value, out temp)) return null;
else return temp;
}
}
public sealed partial class MainPage : Page, INotifyPropertyChanged
{
private int? _serves;
public event PropertyChangedEventHandler PropertyChanged;
public void RaiseProperty(string name) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
public int? Serves
{
get { return _serves; }
set { _serves = value; RaiseProperty("Serves"); }
}
public MainPage()
{
this.InitializeComponent();
DataContext = this;
}
}
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