Question

我是wpf的新手，我目前正在尝试使用网格并添加减法，将元素删除到最终绑定到网格的数据库表。

因此从网格中选择，更新可观察的集合，刷新。

我无法理解如何使用可观察集合的更改通知。

这是我的代码

绑定到网格的类

  public class students
{
   ObservableCollection<GetStudents_Result> stdb = new ObservableCollection<GetStudents_Result>();



   //public event NotifyCollectionChangedEventHandler CollectionChanged;


   public students()
   {


       AbcdEntities abcdEnt=new AbcdEntities();

       List<GetStudents_Result> studentColl = abcdEnt.GetStudents().ToList();
       foreach (var item in studentColl)
       {
           stdb.Add(item);
       }
   }

   //public  void onCollectionChange(object sender,NotifyCollectionChangedEventHandler e)
   //{

   //}

   public ObservableCollection<GetStudents_Result> std {get {return stdb;}}
}

我的xaml。

 <Canvas>
    <TextBox Height="23" Canvas.Top="5" Canvas.Left="10" HorizontalAlignment="Left" Margin="10,10,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" />
    <TextBox Height="23" Canvas.Top="30" Canvas.Left="10" HorizontalAlignment="Left" Margin="10,10,0,0" Name="textBox2" VerticalAlignment="Top" Width="120" />
    <Button Canvas.Left="90" Canvas.Top="65" Content="Remove" Click="button2_Click" Height="23" Name="button2" Width="75" />
    <Button Canvas.Left="10" Canvas.Top="65" Content="Save" Height="23" Name="button1" Width="75" Click="button1_Click" />

    <ListView Name="listviewStudents" Canvas.Top="100" ItemsSource="{Binding std}" SelectionChanged="ListView_SelectionChanged">
        <ListView.View>
            <GridView>                     
                <GridViewColumn Header="fname" DisplayMemberBinding="{Binding Path=fname}"></GridViewColumn>
                <GridViewColumn Header="lname" DisplayMemberBinding="{Binding Path=lname}"></GridViewColumn>
                <GridViewColumn DisplayMemberBinding="{Binding Path=address}"></GridViewColumn>
                <GridViewColumn DisplayMemberBinding="{Binding Path=phno}"></GridViewColumn>
                <GridViewColumn DisplayMemberBinding="{Binding Path=radio}"></GridViewColumn>

            </GridView>

        </ListView.View>

    </ListView>

</Canvas>

我的代码

public MainWindow()
    {
        InitializeComponent();
        students std = new students();
        this.DataContext = std;
    }

    private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {

        GetStudents_Result selectedItem = listviewStudents.SelectedItem as GetStudents_Result;
        textBox1.Text = selectedItem.fname;
        textBox2.Text = selectedItem.lname;


    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        GetStudents_Result selecteditem = listviewStudents.SelectedItem as GetStudents_Result;
        selecteditem.fname = textBox1.Text;
        selecteditem.lname = textBox2.Text;
        listviewStudents.Items.Refresh();
    }

    private void button2_Click(object sender, RoutedEventArgs e)
    {
        listviewStudents.Items.Remove(listviewStudents.SelectedItem);
        listviewStudents.Items.Refresh();
    }
}

}

请原谅任何愚蠢的错误..

Answer 1

这里存在一些问题，您不必触及后面代码中的UI控件，您应该使用数据绑定。

以下是基于帖子的模型绑定的工作示例。

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public MainWindow()
    {
        InitializeComponent();

        // set the DataContext to the code in this window
        this.DataContext = this;

        // create youe Student model
        StudentModel = new students();
    }


    // Create a public property of your student Model
    private students _studentModel;
    public students StudentModel
    { 
        get { return _studentModel; }
        set { _studentModel = value; NotifyPropertyChanged("StudentModel"); }
    }

    // create a public property to use as the selected item from your models "std" collection
    private GetStudents_Result _selectedResult;
    public GetStudents_Result SelectedResult 
    {
        get { return _selectedResult; }
        set { _selectedResult = value; NotifyPropertyChanged("SelectedResult"); }
    }


    private void button2_Click(object sender, RoutedEventArgs e)
    {
        // if you want to remove an item you just have to remove it from
        // the model, the INotifyPropertyChanged interface will notify the UI
        // to update, no need to call Refresh, same works for Add etc
        StudentModel.std.Remove(SelectedResult);
    }


    public event PropertyChangedEventHandler PropertyChanged;
    public void NotifyPropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }
}

现在在xaml我们可以将ListView绑定到您的StudentModel集合和SelectedResult

  <ListView ItemsSource="{Binding StudentModel.std}" SelectedItem="{Binding SelectedResult}" >

对于TextBoxes，您可以绑定到SelectedResult，以便为您更新详细信息

注意：在此示例中，它会在文本更改时更新SelectedResult，您可以根据需要更改它。

<TextBox Text="{Binding SelectedResult.Fname, UpdateSourceTrigger=PropertyChanged}" />
<TextBox Text="{Binding SelectedResult.Lname, UpdateSourceTrigger=PropertyChanged}" />

现在，当您从ListView中选择一个项目时，将会填充这些TextBoxes，并且当这些项目发生更改时，SelectedResult项目将会更改。

现在，要在ListView中添加和删除项目，您只需在StudentModel集合（StudentModel.std）中添加和删除。

private void button2_Click(object sender, RoutedEventArgs e)
{
    StudentModel.std.Remove(SelectedResult);
}

注意：此事件处理程序应该是ICommand绑定，但我会让您搜索：）

这是一个完整的示例，希望有助于解释WPF MVVM

的基础知识

代码：

public partial class MainWindow : Window, INotifyPropertyChanged
{
    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = this;
        StudentModel = new students();
    }

    private students _studentModel;
    public students StudentModel
    { 
        get { return _studentModel; }
        set { _studentModel = value; NotifyPropertyChanged("StudentModel"); }
    }

    private GetStudents_Result _selectedResult;
    public GetStudents_Result SelectedResult 
    {
        get { return _selectedResult; }
        set { _selectedResult = value; NotifyPropertyChanged("SelectedResult"); }
    }

    private void button2_Click(object sender, RoutedEventArgs e)
    {
        StudentModel.std.Remove(SelectedResult);
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void NotifyPropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }
}

public class students
{
    public students()
    {
        std = new ObservableCollection<GetStudents_Result>();
        for (int i = 0; i < 100; i++)
        {
            std.Add(new GetStudents_Result { Fname = "FirstName" + i, Lname = "LasrName" + i });
        }
    }
    public ObservableCollection<GetStudents_Result> std { get; set; }
}

public class GetStudents_Result : INotifyPropertyChanged
{
    private string _fname;
    private string _lname;

    public string Fname
    {
        get { return _fname; }
        set { _fname = value; NotifyPropertyChanged("Fname"); }
    }

    public string Lname
    {
        get { return _lname; }
        set { _lname = value; NotifyPropertyChanged("Lname"); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void NotifyPropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }
}

的Xaml：

 <Canvas>
    <TextBox Text="{Binding SelectedResult.Fname, UpdateSourceTrigger=PropertyChanged}" />
    <TextBox Text="{Binding SelectedResult.Lname, UpdateSourceTrigger=PropertyChanged}" />
    <Button Canvas.Left="90" Canvas.Top="65" Content="Remove" Click="button2_Click" Height="23" Name="button2" Width="75" />
    <Button Canvas.Left="10" Canvas.Top="65" Content="Save" Height="23" Name="button1" Width="75"  />
    <ListView Name="listviewStudents" Canvas.Top="100" ItemsSource="{Binding StudentModel.std}" SelectedItem="{Binding SelectedResult}" >
        <ListView.View>
            <GridView>
                <GridViewColumn Header="fname" DisplayMemberBinding="{Binding Path=Fname}"></GridViewColumn>
                <GridViewColumn Header="lname" DisplayMemberBinding="{Binding Path=Lname}"></GridViewColumn>
            </GridView>
        </ListView.View>
    </ListView>
</Canvas>

我希望此信息有助于：）

Answer 2

首先，如果我做得很差，我会道歉。这是我的第一次尝试。

所以看起来你有正确的想法，你所拥有的大部分内容都会奏效。但看起来您可能忘记实施INotifyPropertyChanged。你可能只考虑使用类似List<GetStudent_Result>的东西，比ObservableCollection少得多，因为你将自己实现NotifyPropertyChanged。

public class students : INotifyPropertyChanged
{

    #region PropertyChanged EventHandler
    public event PropertyChangedEventHandler PropertyChanged;

    void NotifyPropertyChanged(String Property)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(Property));
    }
    #endregion

    private List<GetStudents_Result> stdb;
    public List<GetStudents_Result> std
    {
        get { return stdb; }
        set { stdb = value; NotifyPropertyChanged("std"); }
    }

    ...

如何使用可观察集合并通知属性已更改

2 个答案: