Wpf MVVM中的数据绑定

Question

我是WPF和MVVM中的新成员。

我尝试从mysql数据库获取数据到ObservableCollection然后将其绑定到UI。

问题是，我在Model层的第一个ObservableCollection中有数据，但是当我不能将数据发送到ViewModel层时，所以什么都不会绑定到UI。

class Databasecon 
{ 
    int i = 0; 

    // First Binding for the Database 
    public ObservableCollection<Operator> operators { get; private set; } 

    public Databasecon() 
    { 
     this.operators = new ObservableCollection<Operator>(); 
    } 

    public void Datacon(string conn) 
    { 
     MySqlConnection con = null; 
     MySqlCommand com = null; 
     MySqlDataReader myreader = null; 
     int columnOrdinaloperatorname = -1; 

     con = new MySqlConnection(conn); 
     try 
     { 
      if (com == null) 
      { 
       com = new MySqlCommand("SELECT operator_name FROM operators", con); 
       com.Connection.Open(); 

       myreader = com.ExecuteReader(); 
       columnOrdinaloperatorname = myreader.GetOrdinal("operator_name"); 

       while (myreader.Read()) 
       { 
        this.operators.Add(new Operator() { operatorname = myreader.GetString(columnOrdinaloperatorname).ToString() }); 

        i++; 
       } 
      } 

      MessageBox.Show(operators.Count.ToString()); 
     } 
     catch (MySqlException ex) 
     { 
      MessageBox.Show(ex.ToString()); 
     } 
     finally 
     { 
      if (myreader != null) 
       myreader.Close(); 

      if (com != null) 
      { 
       if (com.Connection != null) 
        com.Connection.Close(); 
      } 
     } 
    } 
} 

class Operator 
{ 
    public string operatorname { get ; set; } 
} 

class collect : INotifyPropertyChanged 
{ 
    private Databasecon databasecon = null; 

    public event PropertyChangedEventHandler PropertyChanged; 

    public ObservableCollection<Operator> operators 
    { 
     get 
     { 
      if (this.databasecon.operators != null) 
      { 
       return this.databasecon.operators;     
      } 
      else 
      { 
       return null; 
      } 
     } 
     set 
     { 
      this.operators = value; RaisePropertyChanged("operators"); 
     } 
    } 

    private void RaisePropertyChanged(string propertyName) 
    { 
     var handler = this.PropertyChanged; 
     if (handler != null) 
     { 
      handler(this, new PropertyChangedEventArgs(propertyName)); 
     } 
    } 

    public collect() 
    { 
     this.databasecon = new Databasecon(); 
    } 
} 

一个的XAML代码是：

<Window.DataContext> 
    <vm:collect/> 
</Window.DataContext> 
<Grid> 
    <TextBlock Margin="459,51,-459,-51"><InlineUIContainer> 
       <TextBlock x:Name="textBlock" TextWrapping="Wrap" Text="{Binding Path=operators}" Width="198" FontSize="28" Height="66"/> 
      </InlineUIContainer></TextBlock> 
    <ListBox x:Name="listBox" HorizontalAlignment="Left" Height="102" Margin="115,240,0,0" VerticalAlignment="Top" Width="339" ItemsSource="{Binding operators}"> 
     <ListBox.ItemTemplate> 
      <DataTemplate> 
       <StackPanel> 
        <TextBlock > 
         <Run Text="{Binding operatorname}"></Run> 
        </TextBlock> 
       </StackPanel> 
      </DataTemplate> 
     </ListBox.ItemTemplate> 
    </ListBox> 

谁能帮助我？

Answer 1

你绑定似乎没什么问题 - 这里就是我所做的测试他们：

<Window.DataContext> 
    <vm:collect/> 
</Window.DataContext> 
<Grid> 
    <Button VerticalAlignment="Top" HorizontalAlignment="Left" Command="{Binding AddThings}" Height="25" Width="Auto">Add Stuff</Button> 
    <TextBlock Margin="459,51,-459,-51"><InlineUIContainer> 
      <TextBlock x:Name="textBlock" TextWrapping="Wrap" Text="{Binding Path=operators}" Width="198" FontSize="28" Height="66"/> 
     </InlineUIContainer></TextBlock> 
    <ListBox x:Name="listBox" HorizontalAlignment="Left" Height="102" Margin="115,240,0,0" VerticalAlignment="Top" Width="339" ItemsSource="{Binding operators}"> 
     <ListBox.ItemTemplate> 
      <DataTemplate> 
       <StackPanel> 
        <TextBlock > 
        <Run Text="{Binding operatorname}"></Run> 
        </TextBlock> 
       </StackPanel> 
      </DataTemplate> 
     </ListBox.ItemTemplate> 
    </ListBox> 
</Grid> 

C＃：

class Databasecon 
{ 
    int i = 0; 

    // First Binding for the Database 
    public ObservableCollection<Operator> operators { get; private set; } 

    public Databasecon() 
    { 
     this.operators = new ObservableCollection<Operator>(); 
    } 

    public void Datacon() 
    { 
      this.operators.Add(new Operator() { operatorname = "Hello world!"}); 
    } 
} 

class Operator 
{ 
    public string operatorname { get; set; } 
} 

class collect : INotifyPropertyChanged 
{ 
    private Databasecon databasecon = null; 

    public event PropertyChangedEventHandler PropertyChanged; 

    public ICommand AddThings { get; set; } 

    public ObservableCollection<Operator> operators 
    { 
     get 
     { 
      if (this.databasecon.operators != null) 
      { 
       return this.databasecon.operators; 
      } 
      else 
      { 
       return null; 
      } 
     } 
     set 
     { 
      this.operators = value; RaisePropertyChanged("operators"); 
     } 
    } 

    private void RaisePropertyChanged(string propertyName) 
    { 
     var handler = this.PropertyChanged; 
     if (handler != null) 
     { 
      handler(this, new PropertyChangedEventArgs(propertyName)); 
     } 
    } 

    public collect() 
    { 
     this.databasecon = new Databasecon(); 
     AddThings = new SimpleCommand(() => databasecon.Datacon()); 
    } 
} 

public class SimpleCommand : ICommand 
{ 
    private Action _command; 

    public SimpleCommand(Action command) 
    { 
     _command = command; 
    } 

    public bool CanExecute(object parameter) 
    { 
     return true; 
    } 

    public event EventHandler CanExecuteChanged; 

    public void Execute(object parameter) 
    { 
     if (_command != null) 
      _command(); 
    } 
} 

您的问题可能在于你设置你的数据上下文的方式。目前，您的窗口在每次实例化时都会创建视图模型的新实例，但由于您没有设置名称，因此我认为此实例仅供窗口使用。你可以把虚拟机的公共属性和调用窗口保持填充集合实例：

<Window.DataContext> 
    <vm:collect x:Name="Collect"/> 
</Window.DataContext> 


window.Collect.Datacon("[My connection string]"); 

或者通过你打算使用的视图模型构造，并设置有实例：

public MainWindow(object viewModel) 
    { 
     DataContext = viewModel; 
     InitializeComponent(); 
    }