c# - UWP:替换数据绑定(bind)

Question

我有一个很奇怪的问题。如果我设置了绑定(bind)并将绑定(bind)更改为另一个属性，它将不起作用。

看看这个简单的例子

lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("Subtotal"), Source = Order, Mode = BindingMode.OneWay });
lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("FinalTotal"), Source = Order, Mode = BindingMode.OneWay });

FinalTotal 更改时，lblTotal 文本将NOT 更改。

现在，注释掉第一行。

//lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("Subtotal"), Source = Order, Mode = BindingMode.OneWay });
lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("FinalTotal"), Source = Order, Mode = BindingMode.OneWay });

现在成功了!!!!更改 FinalTotal 将更改 lblTotal 文本!知道为什么吗？

此外，BindingOperations.ClearBinding() 在 UWP 中不可用。所以我尝试用空绑定(bind)替换它，但它仍然不起作用。

lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("Subtotal"), Source = Order, Mode = BindingMode.OneWay });

//remove binding - not sure if this is correct way to remove binding because
//BindingOperations.ClearBinding() isn't available in UWP!
BindingOperations.SetBinding(lblTotal, TextBlock.TextProperty, new Binding());

lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("FinalTotal"), Source = Order, Mode = BindingMode.OneWay });

我的问题是:1.如何替换UWP中的绑定(bind)？2. 如何删除 UWP 中的现有绑定(bind)(即与 BindingOperations.ClearBinding() 等效的功能)？

感谢您的帮助...

Answer 1

正如在 FrameworkElement.SetBinding method 中声明的那样:

Note Calling the SetBinding method and passing in a new Binding object won't necessarily remove an existing binding. Instead, you should first call the DependencyObject.ClearValue method, then call SetBinding.

因此您可以像下面这样更改您的代码:

lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("Subtotal"), Source = Order, Mode = BindingMode.OneWay });
lblTotal.ClearValue(TextBlock.TextProperty);
lblTotal.SetBinding(TextBlock.TextProperty, new Binding() { Path = new PropertyPath("FinalTotal"), Source = Order, Mode = BindingMode.OneWay });

在此之后您的代码应该能够工作。更多信息，请参见FrameworkElement.SetBinding的备注还有BindingOperations.SetBinding .