使用sql server获取子元素值(get child element value using sql server)

 查看Eric的回答 。 基本上，您将希望使用它来自定义渲染器设置Xamarin Forms Control的属性，而不是直接设置Control的属性。 如果您的Control的属性具有OneWay绑定，则直接从自定义渲染器设置它可能会破坏该绑定。 
 
 在普通的XF ContentPage发生同样的事情。 如果我执行以下操作，则绑定将被第二个赋值覆盖： 
 
Entry entry = new Entry();

entry.SetBinding(Entry.TextProperty, "EntryText"); //Binding is set and good

entry.Text = "blah"; //Binding is overwritten with my hard coded "blah" value
 
 例 
 
 坏： 
 
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
    base.OnElementPropertyChanged(sender, e);

    if (e.PropertyName == Entry.TextProperty.PropertyName) {
        Element.Text = "Overwritten";
    }
}
 
 好： 
 
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
    base.OnElementPropertyChanged(sender, e);

    if (e.PropertyName == Entry.TextProperty.PropertyName) {
        ((IElementController)Element).SetValueFromRenderer(Entry.TextProperty, "Overwritten");
    }
}

Check out Eric's answer. Basically you will want to use that to set your Xamarin Forms Control's property from the custom renderer instead of setting the Control's property directly. If your Control's property has a OneWay binding, setting it directly from the custom renderer could break that binding.
 
The same thing happens in a normal XF ContentPage. If I do the following, the binding gets overwritten with the second assignment:
 
Entry entry = new Entry();

entry.SetBinding(Entry.TextProperty, "EntryText"); //Binding is set and good

entry.Text = "blah"; //Binding is overwritten with my hard coded "blah" value
 
Example
 
Bad:
 
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
    base.OnElementPropertyChanged(sender, e);

    if (e.PropertyName == Entry.TextProperty.PropertyName) {
        Element.Text = "Overwritten";
    }
}
 
Good:
 
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
    base.OnElementPropertyChanged(sender, e);

    if (e.PropertyName == Entry.TextProperty.PropertyName) {
        ((IElementController)Element).SetValueFromRenderer(Entry.TextProperty, "Overwritten");
    }
}