UWP自动填充控件AutoSuggestBox小优化

    UWP提供的AutoSuggestBox本身非常好用，在项目中经常用到，但是当我们使用时发现一下不人性化的设置，例子1如下：

<Page
    x:Class="SelfInkCanvas.AutoBoxTest"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:SelfInkCanvas"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <AutoSuggestBox x:Name="autoSuggestBox" 
                        PlaceholderText="输入一个字符"
                        TextChanged="autoSuggestBox_TextChanged"
                        SuggestionChosen="autoSuggestBox_SuggestionChosen"
                        QuerySubmitted="autoSuggestBox_QuerySubmitted"
                        ></AutoSuggestBox>
    </Grid>
</Page>

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// “空白页”项模板在 http://go.microsoft.com/fwlink/?LinkId=234238 上有介绍

namespace SelfInkCanvas
{
    /// <summary>
    /// 可用于自身或导航至 Frame 内部的空白页。
    /// </summary>
    public sealed partial class AutoBoxTest : Page
    {
        private ObservableCollection<String> suggestions;
        public AutoBoxTest()
        {
            suggestions = new ObservableCollection<string>();
            this.InitializeComponent();
        }

        private void autoSuggestBox_TextChanged(AutoSuggestBox sender, AutoSuggestBoxTextChangedEventArgs args)
         {
                suggestions.Clear();
                suggestions.Add(sender.Text + "1");
                suggestions.Add(sender.Text + "2");
                suggestions.Add(sender.Text + "3");
                suggestions.Add(sender.Text + "4");
                suggestions.Add(sender.Text + "5");
                sender.ItemsSource = suggestions;
            
        }

        private void autoSuggestBox_QuerySubmitted(AutoSuggestBox sender, AutoSuggestBoxQuerySubmittedEventArgs args)
        {

        }

        private void autoSuggestBox_SuggestionChosen(AutoSuggestBox sender, AutoSuggestBoxSuggestionChosenEventArgs args)
        {
        }
    }
}

    当我们输入字符，查找后在输入框会有相应的补充的选项在下面，当我们使用键盘的”↑“和“↓”去选择选项的时候，会发现我们选不了第3项的选项，应为当我们在选择第一个选项的时候，我们发现在我们的输入框中的字符已经变化为选项的内容，这时又会触发autoSuggestBox_TextChanged事件，重新渲染下拉选项，这对于我们使用键盘操作来说是一个不正确的选项。

    所以要求我们的AutoSuggestBox控件在我们选择的时候不会在触发autoSuggestBox_TextChanged事件，只有当我们完成后在使用，因此我们需要对autoSuggestBox_TextChanged事件做一下相应的控制处理。需要明白，当我们选中选项的时候会触发autoSuggestBox_SuggestionChosen事件，而且是每一行多会触发。

   因此我们优化后台代码如下：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// “空白页”项模板在 http://go.microsoft.com/fwlink/?LinkId=234238 上有介绍

namespace SelfInkCanvas
{
    /// <summary>
    /// 可用于自身或导航至 Frame 内部的空白页。
    /// </summary>
    public sealed partial class AutoBoxTest : Page
    {
        private ObservableCollection<String> suggestions;
        bool isChoose = false;
        public AutoBoxTest()
        {
            suggestions = new ObservableCollection<string>();
            this.InitializeComponent();
        }

        private void autoSuggestBox_TextChanged(AutoSuggestBox sender, AutoSuggestBoxTextChangedEventArgs args)
         {
            if (!isChoose)
            {
                suggestions.Clear();
                suggestions.Add(sender.Text + "1");
                suggestions.Add(sender.Text + "2");
                suggestions.Add(sender.Text + "3");
                suggestions.Add(sender.Text + "4");
                suggestions.Add(sender.Text + "5");
                sender.ItemsSource = suggestions;
            }
            isChoose = false;
        }

        private void autoSuggestBox_QuerySubmitted(AutoSuggestBox sender, AutoSuggestBoxQuerySubmittedEventArgs args)
        {

        }

        private void autoSuggestBox_SuggestionChosen(AutoSuggestBox sender, AutoSuggestBoxSuggestionChosenEventArgs args)
        {
            isChoose = true;
        }
    }
}