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尝试基于另一个组合框值将绑定的ObservableCollection筛选到组合框不起作用

collectionviewsource observablecollection wpf c#

MattE · 技术社区 · 6 年前

我看到了一些关于这个的其他帖子,但我似乎不能确切地理解如何让我的使用这个工作正常。

我有两个组合框--角色和位置。

我将这两个都绑定到ObservaleCollection,它在实例化时将枚举值转换为加载到其中的字符串。

<ComboBox  x:Name="empRoleCB" ItemsSource="{Binding Role}" SelectedItem="{Binding RoleStr}"/>
<ComboBox  x:Name="empPositionCB" ItemsSource="{Binding Pos}" SelectedItem="{Binding PosStr}"/>

在我的ViewModel中:

public abstract class EmployeeMenuVMBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected bool SetProperty<T>(ref T field, T newValue, [CallerMemberName] string propertyName = null)
    {
        if(!EqualityComparer<T>.Default.Equals(field, newValue))
        {
            field = newValue;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            return true;
        }
        return false;
    }
}

class EmployeeMenuVM : EmployeeMenuVMBase
{
    private ObservableCollection<string> _pos = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Positions)));
    private ObservableCollection<string> _role = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Roles)));
    public ObservableCollection<string> Pos { get => _pos; }
    public ObservableCollection<string> Role { get => _role; }
    public string RoleStr
    {
        get => _roleStr;
        set => SetProperty(ref _roleStr, value);
    }
    public string PosStr
    {
        get => _posStr;
        set => SetProperty(ref _posStr, value);
    }
}

我想发生的是,当一个角色被选中时,基于这个选择,只应该显示某些位置。例如,如果我选择“客户服务”作为角色,那么职位应该只包含“经理”、“CSS”和“无”。如果角色是“Admin”,那么Position应该只包含“None”,以此类推。

用最少的额外代码或XAML实现这一点的最佳方法是什么?

3 回复 | 直到 6 年前

nadjibnet 6 年前

过滤器 属于 集合视图源

<ComboBox  x:Name="empPositionCB" ItemsSource="{Binding MyPositionFilter}" SelectionChanged="RoleComboBox_SelectionChanged" ....../>


public ICollectionView MyPositionFilter { get; set; }

//ctor
public MyUserControlOrWindow()
{
    //Before InitComponent()
    this.MyPositionFilter = new CollectionViewSource { Source = MyPosObservableCollection }.View;


    InitComponent();
}

public void RoleComboBox_SelectionChanged(object sender,EventArgs e)
{
    //Get the selected Role (the ? is to prevent NullException (VS 2015 >))
    Role r = empRoleCB.SelectedItem as Role;

    //Apply the filter
    this.MyPositionFilter.Filter = item =>
    {
        //Make you sure to convert correcteley your Enumeration, I used it here like a class
        Position p = item as Position;

        //Put your condition here. For example:
        return r.ToLowers().Contains(p.ToLower());

        //Or

        return (r != null && r.Length >= p.Length);
    };
}

过滤器不会更改您的集合,所有隐藏项都保留在ObservableCollection中。

Kip Morgan 6 年前

这一切都可以在ViewModel中完成,方法是在角色更改时更改Positions(Pos)observable集合的值。

class EmployeeMenuVM : EmployeeMenuVMBase
{
    public EmployeeMenuVM()
    {
        var emptyPositions = new List<Global.Positions>()
        { Global.Positions.None };

        _rolePositions.Add(Global.Roles.None, emptyPositions);

        var customerServicePositions = new List<Global.Positions>()
        { Global.Positions.None, Global.Positions.CSS, Global.Positions.Manager };

        _rolePositions.Add(Global.Roles.CustomerService, customerServicePositions);
    }

    private Dictionary<Global.Roles, List<Global.Positions>> _rolePositions = new Dictionary<Global.Roles, List<Global.Positions>>();

    private string _roleStr;
    private string _posStr;

    private ObservableCollection<string> _pos = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Positions)));
    private ObservableCollection<string> _role = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Roles)));

    public ObservableCollection<string> Pos
    {
        get => _pos;

        set
        {
            SetProperty(ref _pos, value);
        }
    }
    public ObservableCollection<string> Role
    {
        get => _role;
    }
    public string RoleStr
    {
        get => _roleStr;
        set
        {
            if (SetProperty(ref _roleStr, value))
            {
                Global.Roles role = (Global.Roles)Enum.Parse(typeof(Global.Roles), value);
                var positions = _rolePositions[role].Select(p => p.ToString());
                Pos = new ObservableCollection<string>(positions);
            }
        }
    }
    public string PosStr
    {
        get => _posStr;
        set => SetProperty(ref _posStr, value);
    }
}

Eibi 6 年前

下面是一个正在运行的测试程序代码,旨在了解如何进行过滤的主要思想:

主窗口.xaml

<Window x:Class="WpfApplication3.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:WpfApplication3"
        x:Name="ThisView"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="600">
    <StackPanel Orientation="Horizontal">
        <ComboBox ItemsSource="{Binding Path=Roles, ElementName=ThisView}" 
                  SelectedItem="{Binding Path=SelectedRole, ElementName=ThisView}"
                  Width="300" Height="60"/>
        <ComboBox ItemsSource="{Binding Path=PositionCollectionView, ElementName=ThisView}" Width="300" Height="60"/>
    </StackPanel>
</Window>

主窗口.xaml.cs

public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public ICollectionView PositionCollectionView { get; set; }

        public ObservableCollection<string> Roles { get; set; } = new ObservableCollection<string>();
        public ObservableCollection<string> Positions { get; set; } = new ObservableCollection<string>();


        private string _selectedRole = String.Empty;

        public string SelectedRole
        {
            get { return _selectedRole; }
            set
            {
                _selectedRole = value;
                OnPropertyChanged();

                //This Refresh activates the Filter again, so that every time you select a role, this property will call it.
                PositionCollectionView.Refresh();

            }
        }

        public MainWindow()
        {
            PositionCollectionView = CollectionViewSource.GetDefaultView(Positions);
            PositionCollectionView.Filter = PositionsFilter;

            //use you enums here
            Roles.Add("Role1");
            Roles.Add("Role2");
            Roles.Add("Role3");
            Roles.Add("Role4");

            Positions.Add("Position1");
            Positions.Add("Position2");
            Positions.Add("Position3");
            Positions.Add("Position4");

            InitializeComponent();
        }

        private bool PositionsFilter(object position)
        {
            bool result = true;

            //place your code according to the Role selected to decide wheather "position" should be in the position list or not

            return result;
        }

        public event PropertyChangedEventHandler PropertyChanged;

        [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }

希望有帮助。。