设置填充数据绑定的单个XAML项的样式

Question

I have a C# ObservableCollection<> that is populating a XAML <ListBox> where each item uses <DataTemplate> . Said list is just a list of date/content pairs where one of the pairs is today's (whatever day you might look at it) date. What I would like to do is give "today's" pair a little "sizzle" (technically, just set .Foreground = (Brush)Resources["PhoneAccentBrush"]; ).

Now, if you notice the /* using ObservableCollection<> chunks, I already accomplished what I was desiring by Insert() . I'm simply wanting to do the same thing, using <DataTemplate> , as it seems like a more appropriate way of coding.

BTW...The only reasons I included the level of code verbosity is that someone would, invariably, ask for more code and the comments might help someone out (I know I've been, greatly, helped by code comments from others).

XAML:

<ListBox x:Name="readingschedule" ItemsSource="{Binding}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBlock FontSize="20" TextWrapping="Wrap" FontWeight="SemiBold" Text="{Binding Date}"/>
                <TextBlock FontSize="27" TextWrapping="Wrap" Margin="0, 0, 0, 20" Text="{Binding Chapter}"/>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>
<!-- replacing with data template
<StackPanel x:Name="readingschedule"/>
-->

C#:

public MainPage()
{
    InitializeComponent();

    // get daily bible reading json results
    dailyBibleReading();

    // data binding for reading schedule
    readingschedule.DataContext = collection_readingschedule;

    // data binding for today's chapter
    todayschapter.DataContext = collection_todayschapter;
}

// create a collection (like an array) for the binding data to be added to
public ObservableCollection<ReadingSchedule> collection_readingschedule = new ObservableCollection<ReadingSchedule>();
// class to define the parts of the collection
public class ReadingSchedule
{
    public ReadingSchedule() { }
    public ReadingSchedule(string date, string chapter)
    {
        Date = date;
        Chapter = chapter;
    }
    public string Date { get; set; }
    public string Chapter { get; set; }
}

// create a collection (like an array) for the binding data to be added to
public ObservableCollection<TodaysChapter> collection_todayschapter = new ObservableCollection<TodaysChapter>();
// class to define the parts of the collection
public class TodaysChapter
{
    public TodaysChapter() { }
    public TodaysChapter(string reference, string text)
    {
        Reference = reference;
        Text = text;
    }
    public string Reference { get; set; }
    public string Text { get; set; }
}

// json connecting and processing example (http://nkishorchandra.blogspot.in/2012/10/parsing-json-in-windows-phone.html)
public void dailyBibleReading()
{
    // the the daily bible reading information for the whole week surrounding today
    DateTime today = DateTime.Today;
    // define default variables
    DateTime begindate = DateTime.Today.AddDays(-7);
    DateTime enddate = DateTime.Today.AddDays(7);
    DayOfWeek day = today.DayOfWeek;
    // redefine variables
    if (day == DayOfWeek.Sunday)
    {
        begindate = DateTime.Today.AddDays(-6);
        enddate = DateTime.Today.AddDays(5);
    }
    if (day == DayOfWeek.Monday)
    {
        begindate = DateTime.Today;
        enddate = DateTime.Today.AddDays(4);
    }
    if (day == DayOfWeek.Tuesday)
    {
        begindate = DateTime.Today.AddDays(-1);
        enddate = DateTime.Today.AddDays(3);
    }
    if (day == DayOfWeek.Wednesday)
    {
        begindate = DateTime.Today.AddDays(-2);
        enddate = DateTime.Today.AddDays(2);
    }
    if (day == DayOfWeek.Thursday)
    {
        begindate = DateTime.Today.AddDays(-3);
        enddate = DateTime.Today.AddDays(1);
    }
    if (day == DayOfWeek.Friday)
    {
        begindate = DateTime.Today.AddDays(-4);
        enddate = DateTime.Today;
    }
    if (day == DayOfWeek.Saturday)
    {
        begindate = DateTime.Today.AddDays(-5);
        enddate = DateTime.Today.AddDays(6);
    }
    string url = "http://www.flcbranson.org/api/dailybiblereading?begindate=" + begindate + "&enddate=" + enddate;

    WebClient dailyBibleReading = new WebClient();
    dailyBibleReading.DownloadStringCompleted += new DownloadStringCompletedEventHandler(dailyBibleReading_DownloadStringCompleted);
    dailyBibleReading.DownloadStringAsync(new Uri(url));
}
void dailyBibleReading_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
    // do something with the feed here
    //string data = e.Result;
    //MessageBox.Show(data);
    // using Json.NET to deserialize the JSON content (http://json.codeplex.com/)
    // don't forget to include "using Newtonsoft.Json;" at the top
    // <RootObject> is the name of a class
    var rootObject = JsonConvert.DeserializeObject<RootObject>(e.Result);

    // used to specify insert position of textblocks (below)
    int schedule_position = 0;
    int fontsize = 27;
    foreach (var chapter in rootObject.dailychapter)
    {
        //MessageBox.Show(chapter.date);
        //MessageBox.Show(chapter.verses[0].text);

        // reading schedule
        // great examples of working with dates (http://www.dotnetperls.com/datetime)
        string chapter_date = chapter.date;
        // Friday, November 3, 2013
        string chapter_date_readable = DateTime.Parse(chapter_date).ToString("D");
        string chapter_book = chapter.book;
        int chapter_chapter = chapter.chapter;
        string chapter_reference = chapter_book + " " + chapter_chapter;
        //MessageBox.Show("The chapter for " + chapter_date_readable + " is " + chapter_reference + ".");

        // Add items to the collection.
        collection_readingschedule.Add(new ReadingSchedule(chapter_date_readable, chapter_reference));

        /* using ObservableCollections<>
        // create new textblocks for each verse (requires an x:Name element to already be present in xaml)
        TextBlock schedule_date = new TextBlock();
        // textblock properties (http://msdn.microsoft.com/en-us/library/system.windows.controls.textblock.fontsize(v=vs.110).aspx)
        schedule_date.Text = chapter_date_readable;
        // font weight names (http://msdn.microsoft.com/en-us/library/windowsphone/develop/system.windows.fontweights(v=vs.105).aspx)
        schedule_date.FontWeight = FontWeights.SemiBold;
        schedule_date.TextWrapping = TextWrapping.Wrap;
        schedule_date.FontSize = fontsize * 0.75;
        // readingschedule is the x:Name that is already present in xaml
        readingschedule.Children.Insert(schedule_position, schedule_date);
        // increment the position
        schedule_position++;

        // create new textblocks for each verse (requires an x:Name element to already be present in xaml)
        TextBlock schedule_reference = new TextBlock();
        // textblock properties (http://msdn.microsoft.com/en-us/library/system.windows.controls.textblock.fontsize(v=vs.110).aspx)
        schedule_reference.Text = chapter_reference;
        schedule_reference.TextWrapping = TextWrapping.Wrap;
        schedule_reference.FontSize = fontsize;
        schedule_reference.Margin = new Thickness(0, 0, 0, fontsize * 0.75);
        // readingschedule is the x:Name that is already present in xaml
        readingschedule.Children.Insert(schedule_position, schedule_reference);
        // increment the position
        schedule_position++;
        */

        // today's chapter
        // 2013-11-03
        string iso8601 = DateTime.Today.ToString("yyyy-MM-dd");
        if (chapter.date == iso8601) {
            /*
            // give today's chapter reference a little pizzaz
            schedule_date.Foreground = (Brush)Resources["PhoneAccentBrush"];
            schedule_reference.Foreground = (Brush)Resources["PhoneAccentBrush"];
            */

            // used to specify insert position of textblocks (below)
            int verse_position = 0;
            foreach (var verse in chapter.verses)
            {
                //MessageBox.Show(verse.text);
                int number = verse.number;
                string text = verse.text;

                // Add items to the collection.
                collection_todayschapter.Add(new TodaysChapter(chapter_reference + ":" + number, text));

                /* using ObservableCollection<>
                // create new textblocks for each verse (requires an x:Name element to already be present in xaml)
                TextBlock verse_reference = new TextBlock();
                // textblock properties (http://msdn.microsoft.com/en-us/library/system.windows.controls.textblock.fontsize(v=vs.110).aspx)
                verse_reference.Text = chapter_reference + ":" + number;
                // font weight names (http://msdn.microsoft.com/en-us/library/windowsphone/develop/system.windows.fontweights(v=vs.105).aspx)
                verse_reference.FontWeight = FontWeights.SemiBold;
                verse_reference.TextWrapping = TextWrapping.Wrap;
                verse_reference.FontSize = fontsize * 0.75;
                // todayschapter is the x:Name that is already present in xaml
                todayschapter.Children.Insert(verse_position, verse_reference);
                // increment the position
                verse_position++;

                // create new textblocks for each verse (requires an x:Name element to already be present in xaml)
                TextBlock verse_text = new TextBlock();
                // textblock properties (http://msdn.microsoft.com/en-us/library/system.windows.controls.textblock.fontsize(v=vs.110).aspx)
                verse_text.Text = text;
                verse_text.TextWrapping = TextWrapping.Wrap;
                verse_text.FontSize = fontsize;
                verse_text.LineHeight = fontsize * 1.25;
                verse_text.Margin = new Thickness(0, 0, 0, fontsize * 0.75);
                // todayschapter is the x:Name that is already present in xaml
                todayschapter.Children.Insert(verse_position, verse_text);
                // increment the position
                verse_position++;
                */
            }
        }
    }
}

// classess for the daily bible reading api json result
// classes generated by json2csharp (http://json2csharp.com)
// generated class names were a little odd so I made them more appropriate
public class Verses
{
    public int number { get; set; }
    public string text { get; set; }
}
public class DailyChapter
{
    public string date { get; set; }
    public string book { get; set; }
    public int chapter { get; set; }
    public List<Verses> verses { get; set; }
}
public class RootObject
{
    public List<DailyChapter> dailychapter { get; set; }
}

Also, if you see something that it just stupid, feel free to point out better ways of doing things. I am very new to C# and XAML. I'm sure that there are better ways of doing what I'm doing. I just don't know them. A lot of it is just hacking away at example code and stuff.

Edit...

Another thread says that DataTemplate.Triggers isn't supported on Windows Phone. Is there another way?

Answer 1

You can use a DataTrigger :

<DataTemplate>
    <StackPanel x:Name="sp">
        <TextBlock FontSize="20" TextWrapping="Wrap" FontWeight="SemiBold" Text="{Binding Date}"/>
        <TextBlock FontSize="27" TextWrapping="Wrap" Margin="0, 0, 0, 20" Text="{Binding Chapter}"/>
    </StackPanel>

    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding Date.Date}" Value="{x:Static sys:DateTime.Today}">
            <Setter TargetName="sp" Property="Background" Value="Red" />
        </DataTrigger>
    </DataTemplate.Triggers>
</DataTemplate>

Answer 2

To make your view models more generic, I would recommend having a Boolean property IsToday in the ReadingSchedule class. So, your ReadingSchedule class would look like this:

public class ReadingSchedule
{
    public ReadingSchedule() { }
    public ReadingSchedule(string date, string chapter)
    {
        Date = date;
        Chapter = chapter;
    }

private bool _isToday;
public bool IsToday
{
    get { return _isToday; }
    private set { _isToday = value; }
}

private string _date;
public string Date 
{
    get { return _date; }
    set
    {
        if (Convert.ToDateTime(value).Day == DateTime.Now.Day)
            IsToday = true;
        _date = value;
    }
}

public string Chapter { get; set; }
}

The change to your view is then as simple as checking for the IsToday value being true with a DataTrigger

<DataTemplate>
    <StackPanel x:Name="sp">
        <TextBlock FontSize="20" TextWrapping="Wrap" FontWeight="SemiBold" Text="{Binding Date}"/>
        <TextBlock FontSize="27" TextWrapping="Wrap" Margin="0, 0, 0, 20" Text="{Binding Chapter}"/>
    </StackPanel>

    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding IsToday}" Value="true">
            <Setter TargetName="sp" Property="Background" Value="Red" />
        </DataTrigger>
    </DataTemplate.Triggers>
</DataTemplate>

I think it's probably better to doit this way than to compare dates in the view, which is less concerned with logic.