WPF IsEnabled Grid

Question

我想讓我的網格在我的屬性爲Null時禁用，並且在非Null時啓用。

在我.XAML：

<Grid Grid.Row="2" IsEnabled="{Binding ElementName=dgCustomers, Path=SelectedItem}"> 
     <my:ProductsHistoryDetailView /> 
    </Grid> 

在我ViewModel.cs：

public ProductHistory SelectedItem 
    { 
     get { return _SelectedItem; } 
     set 
     { 
      if (_SelectedItem != value) 
      { 
       _SelectedItem = value; 
       RaisePropertyChanged(() => SelectedItem); 
      } 
     } 
    } 

Answer 1

你應該額外的屬性添加到您的視圖模型。

public bool IsGridEnabled 
    { 
     get 
      { 
      return this.SelectedItem != null; 
      } 
    } 

<Grid Grid.Row="2" IsEnabled="{Binding IsGridEnabled}"> 
    <my:ProductsHistoryDetailView /> 
</Grid> 

當你的SelectedItem變化，呼籲IsGridEnabled的OnPropertyChanged事件：

public ProductHistory SelectedItem 
{ 
    get { return _SelectedItem; } 
    set 
    { 
     if (_SelectedItem != value) 
     { 
      _SelectedItem = value; 
      RaisePropertyChanged(() => SelectedItem); 
      RaisePropertyChanged(() => IsGridEnabled); 
     } 
    } 
} 

Answer 2

請確保您有selectebitem這樣一個有效值：

<Grid Grid.Row="2" IsEnabled="{Binding ElementName=dgCustomers, Path=SelectedItem.Value}"> 
     <my:ProductsHistoryDetailView /> 
    </Grid> 

Answer 3

你可以使用IValueConverter：

<Grid Grid.Row="2" IsEnabled="{Binding 
    ElementName=dgCustomers, Path=SelectedItem, 
    Converter={StaticResource NullToFalseConverter}"> 

public class NullToFalseConverter : IValueConverter 
{ 
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture) 
    { 
     return value == null ? false : true; 
    } 

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
    { 
     throw new NotImplementedException(); 
    } 
} 

或者，它可能是更容易的另一個屬性IsSelected添加到您的視圖模型，你可以直接綁定到IsEnabled：

public bool IsSelected 
{ 
    get { return _isSelected; } 
    set 
    { 
     if (_isSelected != value) 
     { 
      _isSelected = value; 
      RaisePropertyChanged(() => IsSelected); 
     } 
    } 
} 

public ProductHistory SelectedItem 
{ 
    get { return _SelectedItem; } 
    set 
    { 
     if (_SelectedItem != value) 
     { 
      _SelectedItem = value; 
      RaisePropertyChanged(() => SelectedItem); 
     } 
     IsSelected = value != null; 
    } 
} 

Answer 4

使用樣式觸發改變，而不是試圖直接

<Grid Grid.Row="2"> 
    <Grid.Style> 
     <Style TargetType="Grid"> 
      <Setter Property="IsEnabled" Value="True"/> 
      <Style.Triggers> 
       <DataTrigger Binding="{Binding ElementName=dgCustomers, Path=SelectedItem"}" Value={x:Null}> 
        <Setter Property="IsEnabled" Value="False"/> 
       </DataTrigger> 
      </Style.Triggers>    
     </Style> 
    </Grid.Style> 
</Grid>