小贝子编程

将功能区组合框绑定到导致错误的筛选可观察集合



使用C# 我尝试使用 RibbonRadioButton 过滤 RibbonComboBox 列表，但我无法解决我一直收到的错误。

国家/地区列表位于我使用 ListCollectionView 过滤的可观察集合中。在另一个用户(基于 RadioButton 的 C# WPF 筛选器组合框(的帮助下，我现在让它部分工作，但是如果我单击单选按钮，组合框中的列表会更新，但组合框中没有显示任何内容;我希望显示列表中的第一项。如果我选择一个国家，然后从单选按钮单击另一个大陆，我收到下面显示的错误"公共布尔非洲{...CountryView.Refresh((}'或我点击的任何按钮。[代码于 9 月 25 日更新以反映评论。

功能区组合框错误

Object reference not set to an instance of an object.
In VS Output window:
Error: 40 : BindingExpression path error: 'DisplayName' property not found on 'object'

当我将 XAML 中的功能区组合框更改为组合框时，如下所示，尽管它生成了另一个错误，但它似乎确实可以正常工作。但是，我更喜欢使用RibbonComboBox，但不确定如何解决问题。您可以提供的任何帮助以使其正常工作将不胜感激。

XAML

<Grid>
<DockPanel>
<r:Ribbon DockPanel.Dock="Top" x:Name="Ribbon">
<r:RibbonGroup Header="Continent" Width="260">
<!--<ComboBox x:Name="CountryList" Width="100" ItemsSource="{Binding CountryView}" SelectedItem="{Binding SelectedCountry}" DisplayMemberPath="DisplayName"/>-->
<r:RibbonComboBox x:Name="CountryList" Height="Auto" SelectionBoxWidth="230" VerticalAlignment="Center">
<r:RibbonGallery x:Name="cbSelectedCountry" SelectedValue="{Binding SelectedCountry, Mode=TwoWay}" SelectedValuePath="DisplayName" >
<r:RibbonGalleryCategory x:Name="cbCountryList" ItemsSource="{Binding CountryView}" DisplayMemberPath="DisplayName" />
</r:RibbonGallery>
</r:RibbonComboBox>
<WrapPanel>
<r:RibbonRadioButton x:Name="All" Label="All" GroupName="ContinentGroup" Height="Auto" Width="Auto" HorizontalAlignment="Left" IsChecked="{Binding Path=All}">
</r:RibbonRadioButton>
<r:RibbonRadioButton x:Name="Africa" Label="Africa" GroupName="ContinentGroup" Height="Auto" Width="Auto" HorizontalAlignment="Left" IsChecked="{Binding Path=Africa}">
</r:RibbonRadioButton>
<r:RibbonRadioButton x:Name="America" Label="America" GroupName="ContinentGroup" Height="Auto" Width="Auto" HorizontalAlignment="Left" IsChecked="{Binding Path=America}">
</r:RibbonRadioButton>
</WrapPanel>
</r:RibbonGroup>
</r:Ribbon>
</DockPanel>
</Grid>

C# 代码隐藏 (数据上下文(：

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows.Data;
public class MySettings : INotifyPropertyChanged
{
private readonly ObservableCollection<Country> countries;
private ContinentViewModel selectedContinent;
private static string selectedCountry;
private int selectedRadioGroup;
private ObservableCollection<ContinentViewModel> continents;
private ListCollectionView countryView;
public event PropertyChangedEventHandler PropertyChanged;
private bool _All;
private bool _Africa;
private bool _America;
public bool All { get => _All; set { _All = value; CountryView.Refresh(); SelectedCountry = countries[0].ToString(); } }
public bool Africa { get => _Africa; set { _Africa = value; CountryView.Refresh(); SelectedCountry = countries[0].ToString(); } }
public bool America { get => _America; set { _America = value; CountryView.Refresh(); SelectedCountry = countries[0].ToString(); } }
public MySettings()
{
countries = new ObservableCollection<Country>(
new[]
{
new Country() { Continent = Continent.Africa, DisplayName = "Algeria" },
new Country() { Continent = Continent.Africa, DisplayName = "Egypt" },
new Country() { Continent = Continent.Africa, DisplayName = "Chad" },
new Country() { Continent = Continent.Africa, DisplayName = "Ghana" },
new Country() { Continent = Continent.America, DisplayName = "Canada" },
new Country() { Continent = Continent.America, DisplayName = "Greenland" },
new Country() { Continent = Continent.America, DisplayName = "Haiti" }
});
CountryView = (ListCollectionView)CollectionViewSource.GetDefaultView(countries);
CountryView.Filter += CountryFilter;
Continents = new ObservableCollection<ContinentViewModel>(Enum.GetValues(typeof(Continent)).Cast<Continent>().Select(c => new ContinentViewModel { Model = c }));
}
private bool CountryFilter(object obj)
{
var country = obj as Country;
if (country == null) return false;
if (All) return true;
if (Africa) return country.Continent == Continent.Africa;
if (America) return country.Continent == Continent.America;
return true;
}
public ObservableCollection<ContinentViewModel> Continents
{
get { return continents; }
set
{
continents = value;
}
}
public ListCollectionView CountryView
{
get { return countryView; }
set
{
countryView = value;
}
}
public class Country
{
public string DisplayName { get; set; }
public Continent Continent { get; set; }
}
public enum Continent
{
All,
Africa,
America
}
public class ContinentViewModel
{
public Continent Model { get; set; }
public string DisplayName
{
get
{
return Enum.GetName(typeof(Continent), Model);
}
}
}
public ContinentViewModel SelectedContinent
{
get { return selectedContinent; }
set
{
selectedContinent = value;
OnContinentChanged();
this.OnPropertyChanged("SelectedContinent");
}
}
private void OnContinentChanged()
{
CountryView.Refresh();
}
public int SelectedRadioGroup
{
get { return selectedRadioGroup; }
set
{
selectedRadioGroup = value;
}
}
public string SelectedCountry
{
get { return selectedCountry; }
set
{
if (selectedCountry == value) return;
selectedCountry = value;
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}

我已经修改了您的类来解决您的问题。代码中的更改是：

  1. 而不是CountryView = new ListCollectionView(countries)做CountryView = (ListCollectionView)CollectionViewSource.GetDefaultView(countries)
  2. 在每次刷新列表时，即检查CheckBox时，设置组合框的SelectedItem，即在您的情况下SelectedCountry如下：SelectedCountry = _All ? countries.FirstOrDefault().DisplayName : SelectedCountry;SelectedCountry = _Africa ? countries.Where(_ => _.Continent == Continent.Africa).FirstOrDefault().DisplayName : SelectedCountry;SelectedCountry = _America ? countries.Where(_ => _.Continent == Continent.America).FirstOrDefault().DisplayName : SelectedCountry;

  3. 调用所有属性的OnPropertyChanged。

    private readonly ObservableCollection<Country> countries;
private ContinentViewModel selectedContinent;
private static string selectedCountry;
private int selectedRadioGroup;
private ObservableCollection<ContinentViewModel> continents;
private ListCollectionView countryView;
public event PropertyChangedEventHandler PropertyChanged;
private bool _All;
private bool _Africa;
private bool _America;
public bool All
{
get
{
return _All;
}
set
{
_All = value;
CountryView.Refresh();
SelectedCountry = _All ? countries.FirstOrDefault().DisplayName : SelectedCountry;
OnPropertyChanged("All");
}
}
public bool Africa
{
get
{
return _Africa;
}
set
{
_Africa = value;
CountryView.Refresh();
SelectedCountry = _Africa ? countries.Where(_ => _.Continent == Continent.Africa).FirstOrDefault().DisplayName : SelectedCountry;
OnPropertyChanged("Africa");
}
}
public bool America
{
get
{
return _America;
}
set
{
_America = value;
CountryView.Refresh();
SelectedCountry = _America ? countries.Where(_ => _.Continent == Continent.America).FirstOrDefault().DisplayName : SelectedCountry;
OnPropertyChanged("America");
}
}
public MySettings()
{
countries = new ObservableCollection<Country>(
new[]
{
new Country() { Continent = Continent.Africa, DisplayName = "Algeria" },
new Country() { Continent = Continent.Africa, DisplayName = "Egypt" },
new Country() { Continent = Continent.Africa, DisplayName = "Chad" },
new Country() { Continent = Continent.Africa, DisplayName = "Ghana" },
new Country() { Continent = Continent.America, DisplayName = "Canada" },
new Country() { Continent = Continent.America, DisplayName = "Greenland" },
new Country() { Continent = Continent.America, DisplayName = "Haiti" }
});
CountryView = (ListCollectionView)CollectionViewSource.GetDefaultView(countries);
CountryView.Filter += CountryFilter;
Continents = new ObservableCollection<ContinentViewModel>(Enum.GetValues(typeof(Continent)).Cast<Continent>().Select(c => new ContinentViewModel { Model = c }));
}
private bool CountryFilter(object obj)
{
var country = obj as Country;
if (country == null) return false;
if (All && !Africa && !America) return true;
else if (!All && Africa && !America) return country.Continent == Continent.Africa;
else if (!All && !Africa && America) return country.Continent == Continent.America;
return true;
}
public ObservableCollection<ContinentViewModel> Continents
{
get { return continents; }
set
{
continents = value;
OnPropertyChanged("Continents");
}
}
public ListCollectionView CountryView
{
get { return countryView; }
set
{
countryView = value;
OnPropertyChanged("CountryView");
}
}
public class Country
{
public string DisplayName { get; set; }
public Continent Continent { get; set; }
}
public enum Continent
{
All,
Africa,
America
}
public class ContinentViewModel
{
public Continent Model { get; set; }
public string DisplayName
{
get
{
return Enum.GetName(typeof(Continent), Model);
}
}
}
public ContinentViewModel SelectedContinent
{
get { return selectedContinent; }
set
{
selectedContinent = value;
OnContinentChanged();
this.OnPropertyChanged("SelectedContinent");
}
}
private void OnContinentChanged()
{
CountryView.Refresh();
}
public int SelectedRadioGroup
{
get { return selectedRadioGroup; }
set
{
selectedRadioGroup = value;
OnPropertyChanged("SelectedRadioGroup");
}
}
public string SelectedCountry
{
get { return selectedCountry; }
set
{
if (selectedCountry == value) return;
selectedCountry = value;
OnPropertyChanged("SelectedCountry");
}
}
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

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