实施设计时数据模板时出错 [英] Error Implementing Design Time Data Template
问题描述
我想在WPF GridView
的设计窗口中显示伪数据,并找到一个类似的示例:答案:xaml中数据模板的设计时间数据-堆栈溢出
I want to display dummy data in the design window of a WPF GridView
and found a similar example: Answer: Design time data for datatemplate in xaml - Stack Overflow
我创建了一个新的WPF应用程序(.NET Framework 4.6.1)名为 WpfDataTemplate
,并在示例中的代码段中将其复制到 MainWindow.xaml.cs
和 MainWindow.xaml
。所有添加的内容都在带有 ##
的注释中注明。
I created a new WPF App (.NET Framework 4.6.1) named WpfDataTemplate
and copied in the code snippets from the example into MainWindow.xaml.cs
and MainWindow.xaml
. All additions are noted in comments with ##
.
意外行为:
-
行
< local:MyMockClass x:Key = DesignViewModel />
产生错误对象引用未设置为对象的实例。
The line
<local:MyMockClass x:Key="DesignViewModel" />
produces the error "Object reference not set to an instance of an object."
测试文本#
字符串未显示在设计器中。
The test text #
strings are not displayed in the Designer.
测试文本#
字符串未显示在运行时显示在窗口中。
The test text #
strings are not displayed in the Window at runtime.
问题:
-
错误原因是什么?
What is the cause of the error?
我需要更改什么?使代码按预期工作?
What do I need to change for the code to work as expected?
MainWindow .xaml
<Window x:Class="WpfDataTemplate.MainWindow"
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:WpfDataTemplate"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<!-- ## BEGIN ADD -->
<Window.Resources>
<local:MyMockClass x:Key="DesignViewModel" />
</Window.Resources>
<!-- ## END ADD -->
<Grid>
<!-- ## BEGIN ADD -->
<ListBox x:Name="standardLayoutListBox"
d:DataContext="{Binding Source={StaticResource DesignViewModel}}"
ItemsSource="{Binding MyListBoxItems}">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Label Grid.Column="0" Content="{Binding text1}" />
<Label Grid.Column="1" Content="{Binding text2}" />
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<!-- ## END ADD -->
</Grid>
MainWindow.xaml .cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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;
// ## BEGIN ADD
using System.Collections.ObjectModel;
// ## END ADD
namespace WpfDataTemplate
{
// ## BEGIN ADD
public class MyMockClass
{
public MyMockClass()
{
MyListBoxItems.Add(new MyDataClass() { text1 = "test text 1", text2 = "test text 2" });
MyListBoxItems.Add(new MyDataClass() { text1 = "test text 3", text2 = "test text 4" });
}
public ObservableCollection<MyDataClass> MyListBoxItems { get; set; }
}
public class MyDataClass
{
public string text1 { get; set; }
public string text2 { get; set; }
}
// ## END ADD
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
}
}
推荐答案
首先,您需要在 MyMockClass
中初始化集合。
Firstly you need to initialise your collection in your MyMockClass
.
public class MyMockClass
{
public MyMockClass()
{
MyListBoxItems = new ObservableCollection<MyDataClass>()
MyListBoxItems.Add(new MyDataClass() { text1 = "test text 1", text2 = "test text 2" });
MyListBoxItems.Add(new MyDataClass() { text1 = "test text 3", text2 = "test text 4" });
}
public ObservableCollection<MyDataClass> MyListBoxItems { get; set; }
}
我在Window中使用设计实例,如下所示:
I use the design instance in my Window like so:
d:DataContext="{d:DesignInstance Type=local:MyMockClass, IsDesignTimeCreatable=True}"
这篇关于实施设计时数据模板时出错的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!