[英]IValueConverter not updating Datagrid When Combobox Selection is Changed
我正在嘗試使用 MVVM 原理學習和制作應用程序。 我正在做的是這個,
當嘗試實現 2 個 IValueConverters 時,只有其中一個被觸發,即只有一個被加載和工作,即 OnStockIconConverter,它在 Datagrid 初始化時加載。
另一個是 CurrencyConverter,它依賴於 ComboBox 切換,當我更改所選值時,它不會對 DataGrid 做出反應。
我已經嘗試解決這個問題好幾個小時了,對於 MVVM 初學者來說,那里的大部分內容都相當晦澀。
這里的所有其他問題都與我想做的相反。
C#
namespace Coding_Dojo_3
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
///
///
public partial class MainWindow : Window
{
public ObservableCollection<StockEntryModel> StockEntriesCollection { get; }
public MainWindow()
{
InitializeComponent();
var sampleManager = new SampleManager();
StockEntriesCollection = new ObservableCollection<StockEntryModel>();
foreach (var stockEntry in sampleManager.CurrentStock.OnStock)
{
StockEntriesCollection.Add((new StockEntryModel{SoftwarePackage = stockEntry.SoftwarePackage, Amount = stockEntry.Amount}));
}
DataContext = this;
}
private void ComboBoxCurrency_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var text = ((sender as ComboBox).SelectedItem as ComboBoxItem).Content as string;
SelectedCurrency.Name = text;
Console.WriteLine("Currency changed to {0}", text);
}
}
public class StockEntryModel : INotifyPropertyChanged
{
private object _softwarePackage;
private int _amount;
public event PropertyChangedEventHandler PropertyChanged;
public object SoftwarePackage
{
get => _softwarePackage;
set
{
_softwarePackage = value;
OnPropertyChanged(nameof(SoftwarePackage));
}
}
public int Amount
{
get { return _amount; }
set
{
_amount = value;
OnPropertyChanged(nameof(Amount));
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
public class StockEntryViewModel
{
public StockEntryModel NewStockEntryModel { get; set; }
public StockEntryViewModel()
{
NewStockEntryModel = new StockEntryModel();
}
}
public static class SelectedCurrency
{
public static String Name;
}
public class CurrencyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var currency = SelectedCurrency.Name;
switch (currency)
{
case "EUR":
return CodingDojo4DataLib.Converter.CurrencyConverter.ConvertFromEuroTo(Currencies.EUR,
(double)value);
case "USD":
return CodingDojo4DataLib.Converter.CurrencyConverter.ConvertFromEuroTo(Currencies.EUR,
(double)value);
case "GBP":
return CodingDojo4DataLib.Converter.CurrencyConverter.ConvertFromEuroTo(Currencies.EUR,
(double)value);
default:
return CodingDojo4DataLib.Converter.CurrencyConverter.ConvertFromEuroTo(Currencies.EUR,
(double)value);
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
public class OnStockIconConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is int)
{
if ((int)value < 10)
return "red";
if ((int)value > 10 && (int)value < 20)
return "orange";
if ((int)value > 20)
return "green";
}
return "red";
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
XAML
<Window x:Class="Coding_Dojo_3.MainWindow"
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:local="clr-namespace:Coding_Dojo_3"
mc:Ignorable="d"
Title="Coding Dojo 3" Height="400" Width="1024">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="0.125*" />
<RowDefinition Height="1*" />
<RowDefinition Height="0.125*" />
</Grid.RowDefinitions>
<StackPanel Grid.Row="0" Orientation="Horizontal">
<Label VerticalAlignment="Top">Currency :</Label>
<ComboBox AllowDrop="True" Name="ComboBoxCurrency" VerticalAlignment="Top" SelectionChanged="ComboBoxCurrency_SelectionChanged">
<ComboBoxItem IsSelected="True">EUR</ComboBoxItem>
<ComboBoxItem>USD</ComboBoxItem>
</ComboBox>
</StackPanel>
<DataGrid Grid.Row="1"
Name="DataGridStock"
AutoGenerateColumns="False"
ColumnWidth="*"
x:FieldModifier="public"
IsReadOnly="False"
CanUserAddRows="True"
CanUserDeleteRows="True"
ItemsSource="{Binding StockEntriesCollection}">
<DataGrid.Resources>
<local:CurrencyConverter x:Key="CurrencyConverter"/>
<local:OnStockIconConverter x:Key="OnStockIconConverter"/>
</DataGrid.Resources>
<DataGrid.Columns>
<DataGridTextColumn Header="Name" Binding="{Binding SoftwarePackage.Name}"></DataGridTextColumn>
<DataGridTextColumn Header="Group" Binding="{Binding SoftwarePackage.Category.Name}"></DataGridTextColumn>
<DataGridTextColumn Header="Sales Price" Binding="{Binding SoftwarePackage.SalesPrice, NotifyOnTargetUpdated=True, Converter={StaticResource CurrencyConverter}}"></DataGridTextColumn>
<DataGridTextColumn Header="Purchase Price" Binding="{Binding SoftwarePackage.PurchasePrice, NotifyOnTargetUpdated=True, Converter={StaticResource CurrencyConverter}}"></DataGridTextColumn>
<DataGridTextColumn Header="Amount" Binding="{Binding Amount}"></DataGridTextColumn>
<DataGridTextColumn Header="On Stock" Binding="{Binding Amount, Converter={StaticResource OnStockIconConverter}}"></DataGridTextColumn>
</DataGrid.Columns>
</DataGrid>
<StackPanel Grid.Row="2" Orientation="Horizontal">
<Button Margin="3">Add</Button>
<Button Margin="3">Edit</Button>
<Button Margin="3">Delete</Button>
</StackPanel>
</Grid>
</Window>
您應該將視圖模型和視圖分開,以便您可以使用真正的 MVVM。 現在您的視圖同時也是一個視圖模型。
為了達到目標,向您的入口模型添加一個方法,例如 NotifyAllChanged 以重新計算所有屬性並在您的組合框事件處理程序中調用它。
public class StockEntryModel : INotifyPropertyChanged
{
...
public void NotifyAllChanged()
{
OnPropertyChanged(string.Empty);
}
}
private void ComboBoxCurrency_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var text = ((sender as ComboBox).SelectedItem as ComboBoxItem).Content as string;
SelectedCurrency.Name = text;
Console.WriteLine("Currency changed to {0}", text);
StockEntriesCollection?.ForEach(entry=>entry.NotifyAllChanged()); // <==
}
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