ObservableCollection和DisplayMemberBinding

Question

我試圖填寫ListBoxObservableCollection。但是，當我添加新項目什麼都沒有顯示，只有空項目添加。

有我的代碼片段： XAML

<ListView ItemsSource="{Binding Points}" SelectedItem="{Binding Point}"> 
<ListView.View> 
<GridView AllowsColumnReorder="False"> 
<GridViewColumn Header ="X" Width="100" DisplayMemberBinding = "{Binding Path=ValueX, Mode=TwoWay}" /> 
<GridViewColumn Header ="Y" Width="100" DisplayMemberBinding = "{Binding Path=ValueY, Mode=TwoWay}"/> 
</GridView> 
</ListView.View> 
</ListView> 

Window類

var value = new Value(); 
var viewModel = new ViewModel(value); 
DataContext = viewModel; 
InitializeComponent(); 

值類

private const Point POINT = null; 
private readonly ObservableCollection<Point> _points = new ObservableCollection<Point>(); 
public Value() { 
Point = POINT; 
Points = _points; 
} 

public Point Point { get; set; } 
public ObservableCollection<Point> Points { get; private set; } 
public double ValueX { get; set; } 
public int ValueY { get; set; } 

ViewModel類

private readonly Value _value; 
public ViewModel(Value value) { 
_value = value; 
} 
public Point Point { 
get { return _value.Point; } 
set { 
_value.Point = value; 
OnPropertyChanged("Point"); 
} 
} 

public ObservableCollection<Point> Points { 
get { return _value.Points; } 
} 

private RelayCommand _addCommand; 

     public ICommand AddCommand { 
      get { 
       if (_addCommand == null) { 
        _addCommand = new RelayCommand(Add); 
       } 
       return _addCommand; 
      } 
     } 

     private void Add(object obj) { 
      Points.Add(new Point(ValueX, ValueY)); 
      ValueX = 0; 
      ValueY = 0; 
     } 
public double ValueX { 
     get { 
      return _value.ValueX; 
     } 
     set { 
      if(Math.Abs(_value.ValueX - value) < Mathematics.EPSILON) return; 
      _value.ValueX = value; 
      OnPropertyChanged("ValueX"); 
     } 
    } 

    public int ValueY { 
     get { return _value.ValueY; } 
     set { 
      if(_value.ValueX == value) return; 
      _value.ValueY = value; 
      OnPropertyChanged("ValueY"); 
     } 
    } 

和Point類

public class Point { 
    public readonly double ValueX; 
    public readonly double ValueY; 

    public Point(double valueX, double valueY) { 
     ValueX = valueX; 
     ValueY = valueY; 
    } 

    public override string ToString() { 
     return (ValueX + " " + ValueY); 
    } 
} 

當我嘗試添加新項目，新項目將被添加，但不顯示任何內容。什麼原因可以在這裏？

Answer 1

由於綁定ItemsSource到ObservableCollection<Point>這意味着每個項目是具有ValueX和ValueY聲明爲哪些不是有效綁定源字段Point類型。將它們更改爲屬性：

public double ValueX { get; private set; } 
public double ValueY { get; private set; } 

除了使用Mode=TwoWay以外的東西是隻讀的。這應該更改爲OneWay。如果你想離開TwoWay綁定，然後從setter刪除private，但你也需要更改GridViewColumn.CellTemplate爲TextBox，而不是使用DisplayMemberBinding這是僅用於顯示。