我是WPF，通用应用程序等的新开发人员。
我创建了一个显示问题的视图。
我有一个QuestionsViewModel，它公开了一个Question集合。在XAML中，我使用ItemsControl来显示问题。
现在在DataTemplate中，我想使用一个用户控件来显示问题，实例化我的QuestionViewModel，将当前Question绑定到该问题，并将视图模型设置为该用户控件的上下文。我的问题是{Binding}没有给我一个问题，我有一个Binding对象：/
我应该那样做吗？
如何在ViewModel中获取当前的Question？
码
public class Question : AEntity, IQuestion
{
public Question(String title, String answer) : base()
{
this.Title = title;
this.Answer = answer;
}
public string Title { get; set; }
public string Answer { get; set; }
}
public class QuestionsViewModel : BaseViewModel
{
private String description;
public QuestionsViewModel()
{
ObservableCollection<Question> questions = new ObservableCollection<Question>();
questions.CollectionChanged += Questions_CollectionChanged;
Questions = questions;
AddQuestionCommand = new AddQuestionCommand(Questions);
AddQuestionCommand.Execute(null);//add a question for test
}
private void Questions_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
Description = String.Format("{0} question(s)", Questions.Count);
}
public ICollection<Question> Questions { get; private set; }
public ICommand AddQuestionCommand { get; private set; }
public String Description {
get { return description; }
set
{
description = value;
onPropertyChanged("Description");
}
}
}
public class QuestionViewModel : BaseViewModel
{
private Question question;
public QuestionViewModel()
{
}
public Question Question { get; set; }
}
问题视图
<UserControl x:Class="Question_Answer.View.Control.QuestionsControl"
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:model="using:Question_Answer.Model"
xmlns:uc="using:Question_Answer.View.Control"
xmlns:vm="using:Question_Answer.ViewModel.Control"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<UserControl.DataContext>
<vm:QuestionsViewModel Description="view description"> </vm:QuestionsViewModel>
</UserControl.DataContext>
<ItemsControl Name="Questions" Grid.Row="1" Grid.ColumnSpan="2" ItemsSource="{Binding Questions}">
<ItemsControl.ItemTemplate>
<DataTemplate x:DataType="model:Question">
<uc:QuestionItemControl>
<uc:QuestionItemControl.DataContext>
<vm:QuestionViewModel Question="{Binding}" />
</uc:QuestionItemControl.DataContext>
</uc:QuestionItemControl>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</UserControl>
问题用户控制
<UserControl
x:Class="Question_Answer.View.Control.QuestionItemControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Question_Answer.View.Control"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Text="{Binding Question.Title}" />
<TextBlock Grid.Column="1" Text="{Binding Question.Answer}" />
</Grid>
最佳答案
您的代码中需要修改一些内容。
我直接制作一个代码示例供您参考。
public class QuestionsViewModel:ViewModelBase
{
private String description;
public ObservableCollection<Question> questions { get; set; }
public QuestionsViewModel()
{
questions = new ObservableCollection<Question>();
questions.CollectionChanged += Questions_CollectionChanged;
questions.Add(new Question("t1","a1"));
}
private void Questions_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
Description = String.Format("{0} question(s)", e.NewItems.Count);
}
public String Description
{
get { return description; }
set
{
description = value;
RaisePropertyChanged("Description");
}
}
}
public class QuestionViewModel:ViewModelBase
{
private Question question;
public QuestionViewModel()
{
}
public Question Question
{
get { return question; }
set
{
question = value;
RaisePropertyChanged("Question");
}
}
}
<UserControl
x:Class="AppMvvm2.QuestionItemControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:AppMvvm2"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Text="{Binding Title}" />
<TextBlock Grid.Column="1" Text="{Binding Answer}" />
</Grid>
<UserControl
x:Class="AppMvvm2.QuestionsControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:AppMvvm2"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<UserControl.DataContext>
<local:QuestionsViewModel></local:QuestionsViewModel>
</UserControl.DataContext>
<StackPanel Margin="0 50 0 0">
<TextBlock Text="{Binding Description}"></TextBlock>
<ItemsControl Name="Questions" Grid.Row="1" Grid.ColumnSpan="2" ItemsSource="{Binding questions}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<local:QuestionItemControl></local:QuestionItemControl>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
<Page
x:Class="AppMvvm2.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:AppMvvm2"
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}">
<local:QuestionsControl></local:QuestionsControl>
</Grid>