[英]IValueConverter not updating Datagrid When Combobox Selection is Changed
我正在尝试使用 MVVM 原理学习和制作应用程序。 我正在做的是这个,
当尝试实现 2 个 IValueConverters 时,只有其中一个被触发,即只有一个被加载和工作,即 OnStockIconConverter,它在 Datagrid 初始化时加载。
另一个是 CurrencyConverter,它依赖于 ComboBox 切换,当我更改所选值时,它不会对 DataGrid 做出反应。
我已经尝试解决这个问题好几个小时了,对于 MVVM 初学者来说,那里的大部分内容都相当晦涩。
这里的所有其他问题都与我想做的相反。
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>
您应该将视图模型和视图分开,以便您可以使用真正的 MVVM。 现在您的视图同时也是一个视图模型。
为了达到目标,向您的入口模型添加一个方法,例如 NotifyAllChanged 以重新计算所有属性并在您的组合框事件处理程序中调用它。
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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