尽管“使用最终值”正确，WPF 绑定仍无法正常工作答案

【问题标题】：WPF binding not working despite correct "using final value"尽管“使用最终值”正确，WPF 绑定仍无法正常工作
【发布时间】：2017-07-14 14:41:38
【问题描述】：

我有一个绑定到 ViewModel 的属性 MinDuration 的 TextBox。并且 MinDuration 始终应该小于或等于 ViewModel 的 Duration 属性。所以，我的 XAML：

<TextBox Text="{Binding BasePO.MinDuration, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

还有我的财产：

    private double minDuration;
    public double MinDuration
    {
        get { return minDuration; }
        set
        {
            if (value > Duration)
               minDuration = Duration;
            else
                minDuration = value;

            OnPropertyChanged("MinDuration");
        }
    }

所以，让 Duration = 40。现在，这是绑定的结果：

如果我输入 4 -> TextBox 显示 4
如果然后我输入 5（现在的值为 45）-> TextBox 显示 40（正确！）

但是，问题来了：

如果我输入 4 -> TextBox 显示 4
if then I put 0 (value is now 40) -> TextBox 显示 40
如果然后我输入例如 5（现在的值为 405）-> TextBox 显示 405（Why???）

有绑定痕迹：

System.Windows.Data Warning: 90 : BindingExpression (hash=22334206): Update - got raw value '4'
System.Windows.Data Warning: 93 : BindingExpression (hash=22334206): Update - implicit converter produced '4'
System.Windows.Data Warning: 94 : BindingExpression (hash=22334206): Update - using final value '4'
System.Windows.Data Warning: 102 : BindingExpression (hash=22334206): SetValue at level 1 to PO (hash=59829654) using RuntimePropertyInfo(MinDuration): '4'
System.Windows.Data Warning: 95 : BindingExpression (hash=22334206): Got PropertyChanged event from PO (hash=59829654)
System.Windows.Data Warning: 101 : BindingExpression (hash=22334206): GetValue at level 0 from PoTableForm (hash=53931641) using RuntimePropertyInfo(BasePO): PO (hash=59829654)
System.Windows.Data Warning: 101 : BindingExpression (hash=22334206): GetValue at level 1 from PO (hash=59829654) using RuntimePropertyInfo(MinDuration): '4'
System.Windows.Data Warning: 80 : BindingExpression (hash=22334206): TransferValue - got raw value '4'
System.Windows.Data Warning: 84 : BindingExpression (hash=22334206): TransferValue - implicit converter produced '4'
System.Windows.Data Warning: 89 : BindingExpression (hash=22334206): TransferValue - using final value '4'
Поток '<Без имени>' (0x19b4) завершился с кодом 0 (0x0).


System.Windows.Data Warning: 90 : BindingExpression (hash=22334206): Update - got raw value '45'
System.Windows.Data Warning: 93 : BindingExpression (hash=22334206): Update - implicit converter produced '45'
System.Windows.Data Warning: 94 : BindingExpression (hash=22334206): Update - using final value '45'
System.Windows.Data Warning: 102 : BindingExpression (hash=22334206): SetValue at level 1 to PO (hash=59829654) using RuntimePropertyInfo(MinDuration): '45'
System.Windows.Data Warning: 95 : BindingExpression (hash=22334206): Got PropertyChanged event from PO (hash=59829654)
System.Windows.Data Warning: 101 : BindingExpression (hash=22334206): GetValue at level 0 from PoTableForm (hash=53931641) using RuntimePropertyInfo(BasePO): PO (hash=59829654)
System.Windows.Data Warning: 101 : BindingExpression (hash=22334206): GetValue at level 1 from PO (hash=59829654) using RuntimePropertyInfo(MinDuration): '40'
System.Windows.Data Warning: 80 : BindingExpression (hash=22334206): TransferValue - got raw value '40'
System.Windows.Data Warning: 84 : BindingExpression (hash=22334206): TransferValue - implicit converter produced '40'
System.Windows.Data Warning: 89 : BindingExpression (hash=22334206): TransferValue - using final value '40'


System.Windows.Data Warning: 90 : BindingExpression (hash=22334206): Update - got raw value '405'
System.Windows.Data Warning: 93 : BindingExpression (hash=22334206): Update - implicit converter produced '405'
System.Windows.Data Warning: 94 : BindingExpression (hash=22334206): Update - using final value '405'
System.Windows.Data Warning: 102 : BindingExpression (hash=22334206): SetValue at level 1 to PO (hash=59829654) using RuntimePropertyInfo(MinDuration): '405'
System.Windows.Data Warning: 95 : BindingExpression (hash=22334206): Got PropertyChanged event from PO (hash=59829654)
System.Windows.Data Warning: 101 : BindingExpression (hash=22334206): GetValue at level 0 from PoTableForm (hash=53931641) using RuntimePropertyInfo(BasePO): PO (hash=59829654)
System.Windows.Data Warning: 101 : BindingExpression (hash=22334206): GetValue at level 1 from PO (hash=59829654) using RuntimePropertyInfo(MinDuration): '40'
System.Windows.Data Warning: 80 : BindingExpression (hash=22334206): TransferValue - got raw value '40'
System.Windows.Data Warning: 84 : BindingExpression (hash=22334206): TransferValue - implicit converter produced '40'
System.Windows.Data Warning: 89 : BindingExpression (hash=22334206): TransferValue - using final value '40'

如您所见，当我输入 405 使用最终值 '40'，但 TextBox 显示 405。并且绑定不适用于以 40 开头的每个数字（在此示例中）。 p>

【问题讨论】：

您的目标是哪个版本的框架？
我的 .net 版本是 4.0
请记得给有用的答案投票 :) stackoverflow.com/help/someone-answers

标签： wpf mvvm binding

【解决方案1】：

这实际上是一个已在 .NET Framework 4.5 中修复的旧错误。请在此处参考@Matt 的回答以获取更多信息。

Bound WPF TextBox is not updating value when the bound property enforces some business rules

如果由于某些原因无法升级到 4.5，您可能需要尝试此处建议的解决方法：

WPF - MVVM - Textbox getting out of sync with viewmodel property

应该提到的是，官方支持的 .NET Framework 的最旧版本目前是 4.5.2，所以毕竟升级可能是一个想法：https://blogs.msdn.microsoft.com/dotnet/2015/12/09/support-ending-for-the-net-framework-4-4-5-and-4-5-1/

【讨论】：