属性触发器无效

Question

我正在使用Xamarin.Forms，其中我在代码后面使用了属性触发器，所有编码都已完成。请帮我解决我在代码中犯的错误。

Label header = new Label
{
   Text = "Trigger",
   Font = Font.BoldSystemFontOfSize(50),
   HorizontalOptions = LayoutOptions.Center
};

Entry enter = new Entry
{
    Placeholder = "Enter Name"
};

Trigger trigger = new Trigger(typeof(Entry))
{
    Property = Entry.IsFocusedProperty,
    Value = "True"
};

trigger.Setters.Add(new Setter
{
    Property = VisualElement.BackgroundColorProperty,
    Value = Color.Red
});

enter.Triggers.Add(trigger);

this.Content = new StackLayout
{
    Children = 
    {
        header,
        enter
    }
};

仅触发器部件无法正常工作