示例

MainWindow.xaml

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:WpfTest"
    xmlns:Properties="clr-namespace:WpfTest.Properties"
    xmlns:wpf="http://schemas.microsoft.com/netfx/2007/xaml/presentation" x:Class="WpfTest.MainWindow"
    mc:Ignorable="d"
    Title="MainWindow" Height="250" Width="400">
    <!--资源通常定义在根节点，或者资源字典中-->
    <Window.Resources>
        <DataTemplate x:Key="myTaskTemplate">
            <Border Name="border" BorderBrush="Aqua" BorderThickness="1"
                Padding="5" Margin="5" Width="250">
                <StackPanel>
                    <TextBlock Text="{Binding Path=TaskName}"/>
                    <TextBlock Text="{Binding Path=Description}"/>
                    <TextBlock Text="{Binding Path=Priority}"/>
                </StackPanel>
            </Border>
        </DataTemplate>
    </Window.Resources>
    
    <Grid>
        <ListBox Name="listBox" Width="300" Margin="10"
         ItemTemplate="{StaticResource myTaskTemplate}"/>
    </Grid>
</Window>

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;//INotifyPropertyChanged
using System.Threading.Tasks;

namespace WpfTest
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public List<ItemData> myTodoList;

        public MainWindow()
        {
            InitializeComponent();

            List<ItemData> list = new List<ItemData>();
            list.Add(new ItemData { TaskName = "A", Description = "aaa", Priority = 1 });
            list.Add(new ItemData { TaskName = "B", Description = "bbb", Priority = 2 });
            list.Add(new ItemData { TaskName = "C", Description = "ccc", Priority = 3 });
            this.listBox.ItemsSource = list;
        }
    }

    public class ItemData
    {
        // 注意：
        // 字段无法直接数据绑定
        // 只有属性才能与{Binding Path=*}绑定
        public string TaskName { get; set; }
        public string Description { get; set; }
        public int Priority { get; set; }
    }
}

运行测试