C# 如何在启动或筛选后始终展开treeview中的前2个节点

我有一个带有mvvm和集合的示例项目来构建树状视图

我想知道如何实现总是展开前2个节点时启动或过滤后的树视图

XAML

视图模型

public class MainWindowViewModel : PropertyChangedBase
{
    private bool _isDisplayGreen = true;
    private bool _isDisplayRed = true;
    private bool _isDisplayYellow = true;

    public bool IsDisplayGreen
    {
        get { return _isDisplayGreen; }
        set
        {
            _isDisplayGreen = value;
            FilterFunction();
            OnPropertyChanged("IsDisplayRed");
            OnPropertyChanged("IsDisplayGreen");
            OnPropertyChanged("IsDisplayYellow");
        }
    }

    public bool IsDisplayRed
    {
        get { return _isDisplayRed; }
        set
        {
            _isDisplayRed = value;
            FilterFunction();
            OnPropertyChanged("IsDisplayRed");
            OnPropertyChanged("IsDisplayGreen");
            OnPropertyChanged("IsDisplayYellow");
        }
    }

    public bool IsDisplayYellow
    {
        get { return _isDisplayYellow; }
        set
        {
            if (value == false)
            {
                _isDisplayGreen = value;
            }

            _isDisplayYellow = value;
            FilterFunction();
            OnPropertyChanged("IsDisplayRed");
            OnPropertyChanged("IsDisplayGreen");
            OnPropertyChanged("IsDisplayYellow");
        }
    }

    private void FilterFunction()
    {
        ICollectionView classesDataSourceView = CollectionViewSource.GetDefaultView(ClassList);

        classesDataSourceView.Filter = (classModel =>
        {
            ICollectionView studentsDataSourceView = CollectionViewSource.GetDefaultView(((Class)classModel).Students);

            if (_isDisplayGreen == false && _isDisplayYellow == false && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => false);
            }

            if (_isDisplayGreen == true && _isDisplayYellow == true && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => true);
            }

            if (_isDisplayGreen == false && _isDisplayYellow == true && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Yellow-icon.png"));
            }

            if (_isDisplayGreen == true && _isDisplayYellow == false && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Green-icon.png"));
            }

            if (_isDisplayGreen == false && _isDisplayYellow == false && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Red-icon.png"));
            }

            if (_isDisplayGreen == true && _isDisplayYellow == false && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Red-icon.png") || ((Student)studentModel).ImagePath.Equals("../Images/Green-icon.png"));
            }

            if (_isDisplayGreen == false && _isDisplayYellow == true && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Red-icon.png") || ((Student)studentModel).ImagePath.Equals("../Images/Yellow-icon.png"));
            }

            if (_isDisplayGreen == true && _isDisplayYellow == true && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Yellow-icon.png") || ((Student)studentModel).ImagePath.Equals("../Images/Green-icon.png"));
            }

            return !studentsDataSourceView.IsEmpty;
        });
    }

    private ObservableCollection<Class> classList;

    public ObservableCollection<Class> ClassList
    {
        get { return classList; }
        set { classList = value; }
    }

    public MainWindowViewModel()
    {
        classList = GetAll();
    }

    public ObservableCollection<Class> GetAll()
    {
        ObservableCollection<Class> classList = new ObservableCollection<Class>();
        Class treeItem = null;
        string greenIconPath = "../Images/Green-icon.png";
        string redIconPath = "../Images/Red-icon.png";
        string yellowIconPath = "../Images/Yellow-icon.png";

        treeItem = new Class("Class A", redIconPath);
        treeItem.Students.Add(new Student("Student 1", greenIconPath));
        treeItem.Students.Add(new Student("Student 2", greenIconPath));
        treeItem.Students.Add(new Student("Student 3", redIconPath));
        classList.Add(treeItem);

        treeItem = new Class("Class B", yellowIconPath);
        treeItem.Students.Add(new Student("Student 1", yellowIconPath));
        treeItem.Students.Add(new Student("Student 2", greenIconPath));
        treeItem.Students.Add(new Student("Student 3", greenIconPath));
        classList.Add(treeItem);

        treeItem = new Class("Class C", greenIconPath);
        treeItem.Students.Add(new Student("Student 1", greenIconPath));
        treeItem.Students.Add(new Student("Student 2", greenIconPath));
        treeItem.Students.Add(new Student("Student 3", greenIconPath));
        classList.Add(treeItem);

        return classList;
    }
}

公共类MainWindowViewModel:PropertyChangedBase { 私有bool_isDisplayGreen=true； 私有bool_isdisplayed=true； 私有bool_isdisplayellow=真； 公共图书馆显示绿色 { 获取{return\u isDisplayGreen；} 设置 { _isDisplayGreen=值； FilterFunction（）； 不动产变更（“显示”）； OnPropertyChanged（“IsDisplayGreen”）； OnPropertyChanged（“IsDisplayYellow”）； } } 显示公共布尔值 { 获取{return\u isdisplayed；} 设置 { _isDisplayRed=值； FilterFunction（）； 不动产变更（“显示”）； OnPropertyChanged（“IsDisplayGreen”）； OnPropertyChanged（“IsDisplayYellow”）； } } 公共广播显示黄色 { 获取{return\u isdisplayellow；} 设置 { 如果（值==false） { _isDisplayGreen=值； } _isDisplayYellow=数值； FilterFunction（）； 不动产变更（“显示”）； OnPropertyChanged（“IsDisplayGreen”）； OnPropertyChanged（“IsDisplayYellow”）； } } 私有void FilterFunction（） { ICollectionView类DataSourceView=CollectionViewSource.GetDefaultView（类列表）； classesDataSourceView.Filter=（classModel=> { ICollectionView学生SDataSourceView=CollectionViewSource.GetDefaultView（（（类）类模型）.Students）； 如果（_isDisplayGreen==false&&u isDisplayYellow==false&&u isDisplayRed==false） { studentsDataSourceView.Filter=（studentModel=>false）； } 如果（_isDisplayGreen==true&&&u isDisplayYellow==true&&u isDisplayRed==true） { studentsDataSourceView.Filter=（studentModel=>true）； } 如果（_isDisplayGreen==false&&u isDisplayYellow==true&&u isDisplayRed==false） { studentsDataSourceView.Filter=（studentModel=>（（Student）studentModel.ImagePath.Equals（“../Images/Yellow icon.png”）； } 如果（_isDisplayGreen==true&&u isDisplayYellow==false&&u isDisplayRed==false） { studentsDataSourceView.Filter=（studentModel=>（（Student）studentModel.ImagePath.Equals（“../Images/Green-icon.png”）； } 如果（_isDisplayGreen==false&&u isDisplayYellow==false&&u isDisplayRed==true） { studentsDataSourceView.Filter=（studentModel=>（（Student）studentModel.ImagePath.Equals（“../Images/Red icon.png”）； } 如果（_isDisplayGreen==true&&&u isDisplayYellow==false&&u isDisplayRed==true） { studentsDataSourceView.Filter=（studentModel=>（（学生）studentModel.ImagePath.Equals（“../Images/Red-icon.png”）| |（（学生）studentModel.ImagePath.Equals（“../Images/Green-icon.png”）； } 如果（_isDisplayGreen==false&&u isDisplayYellow==true&&u isDisplayRed==true） { studentsDataSourceView.Filter=（studentModel=>（（学生）studentModel.ImagePath.Equals（“../Images/Red icon.png”）| |（（学生）studentModel.ImagePath.Equals（“../Images/Yellow icon.png”）； } 如果（_isDisplayGreen==true&&&u isDisplayYellow==true&&u isDisplayRed==false） { studentsDataSourceView.Filter=（studentModel=>（（学生）studentModel.ImagePath.Equals（“../Images/Yellow icon.png”）| |（（学生）studentModel.ImagePath.Equals（“../Images/Green icon.png”）； } return！studentsDataSourceView.IsEmpty； }); } 私有可观测集合类列表； 公共ObservableCollection类列表 { 获取{return classList；} 设置{classList=value；} } 公共主窗口视图模型（） { classList=GetAll（）； } 公共可观测集合GetAll（） { ObservableCollection类列表=新的ObservableCollection（）； 类treeItem=null； 字符串greenIconPath=“../Images/Green-icon.png”； 字符串redIconPath=“../Images/Red icon.png”； 字符串yellowIconPath=“../Images/Yellow icon.png”； treeItem=新类（“A类”，redIconPath）； 添加（新学生（“学生1”，绿色图标））； 添加（新学生（“学生2”，绿色图标））； 添加（新学生（“学生3”，redIconPath））； classList.Add（treeItem）； treeItem=新类别（“B类”，黄色图标）； 添加（新学生（“学生1”，黄色图标））； 添加（新学生（“学生2”，绿色图标））； 添加（新学生（“学生3”，绿色图标））； classList.Add（treeItem）； treeItem=新类别（“C类”，绿色通道）； 添加（新学生（“学生1”，绿色图标））； 添加（新学生（“学生2”，绿色图标））； 添加（新学生（“学生3”，绿色图标））； classList.Add（treeItem）； 返回类列表； } }

---

您可以通过绑定来完成此操作。使用树视图，它可以

public class MainWindowViewModel : PropertyChangedBase
{
    private bool _isDisplayGreen = true;
    private bool _isDisplayRed = true;
    private bool _isDisplayYellow = true;

    public bool IsDisplayGreen
    {
        get { return _isDisplayGreen; }
        set
        {
            _isDisplayGreen = value;
            FilterFunction();
            OnPropertyChanged("IsDisplayRed");
            OnPropertyChanged("IsDisplayGreen");
            OnPropertyChanged("IsDisplayYellow");
        }
    }

    public bool IsDisplayRed
    {
        get { return _isDisplayRed; }
        set
        {
            _isDisplayRed = value;
            FilterFunction();
            OnPropertyChanged("IsDisplayRed");
            OnPropertyChanged("IsDisplayGreen");
            OnPropertyChanged("IsDisplayYellow");
        }
    }

    public bool IsDisplayYellow
    {
        get { return _isDisplayYellow; }
        set
        {
            if (value == false)
            {
                _isDisplayGreen = value;
            }

            _isDisplayYellow = value;
            FilterFunction();
            OnPropertyChanged("IsDisplayRed");
            OnPropertyChanged("IsDisplayGreen");
            OnPropertyChanged("IsDisplayYellow");
        }
    }

    private void FilterFunction()
    {
        ICollectionView classesDataSourceView = CollectionViewSource.GetDefaultView(ClassList);

        classesDataSourceView.Filter = (classModel =>
        {
            ICollectionView studentsDataSourceView = CollectionViewSource.GetDefaultView(((Class)classModel).Students);

            if (_isDisplayGreen == false && _isDisplayYellow == false && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => false);
            }

            if (_isDisplayGreen == true && _isDisplayYellow == true && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => true);
            }

            if (_isDisplayGreen == false && _isDisplayYellow == true && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Yellow-icon.png"));
            }

            if (_isDisplayGreen == true && _isDisplayYellow == false && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Green-icon.png"));
            }

            if (_isDisplayGreen == false && _isDisplayYellow == false && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Red-icon.png"));
            }

            if (_isDisplayGreen == true && _isDisplayYellow == false && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Red-icon.png") || ((Student)studentModel).ImagePath.Equals("../Images/Green-icon.png"));
            }

            if (_isDisplayGreen == false && _isDisplayYellow == true && _isDisplayRed == true)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Red-icon.png") || ((Student)studentModel).ImagePath.Equals("../Images/Yellow-icon.png"));
            }

            if (_isDisplayGreen == true && _isDisplayYellow == true && _isDisplayRed == false)
            {
                studentsDataSourceView.Filter = (studentModel => ((Student)studentModel).ImagePath.Equals("../Images/Yellow-icon.png") || ((Student)studentModel).ImagePath.Equals("../Images/Green-icon.png"));
            }

            return !studentsDataSourceView.IsEmpty;
        });
    }

    private ObservableCollection<Class> classList;

    public ObservableCollection<Class> ClassList
    {
        get { return classList; }
        set { classList = value; }
    }

    public MainWindowViewModel()
    {
        classList = GetAll();
    }

    public ObservableCollection<Class> GetAll()
    {
        ObservableCollection<Class> classList = new ObservableCollection<Class>();
        Class treeItem = null;
        string greenIconPath = "../Images/Green-icon.png";
        string redIconPath = "../Images/Red-icon.png";
        string yellowIconPath = "../Images/Yellow-icon.png";

        treeItem = new Class("Class A", redIconPath);
        treeItem.Students.Add(new Student("Student 1", greenIconPath));
        treeItem.Students.Add(new Student("Student 2", greenIconPath));
        treeItem.Students.Add(new Student("Student 3", redIconPath));
        classList.Add(treeItem);

        treeItem = new Class("Class B", yellowIconPath);
        treeItem.Students.Add(new Student("Student 1", yellowIconPath));
        treeItem.Students.Add(new Student("Student 2", greenIconPath));
        treeItem.Students.Add(new Student("Student 3", greenIconPath));
        classList.Add(treeItem);

        treeItem = new Class("Class C", greenIconPath);
        treeItem.Students.Add(new Student("Student 1", greenIconPath));
        treeItem.Students.Add(new Student("Student 2", greenIconPath));
        treeItem.Students.Add(new Student("Student 3", greenIconPath));
        classList.Add(treeItem);

        return classList;
    }
}

<TreeView ItemsSource="{Binding ClassList}">
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="{Binding Path=IsExpanded, Mode=TwoWay}"/>
        </Style>
    </TreeView.ItemContainerStyle>
    <TreeView.Resources>
        <HierarchicalDataTemplate DataType="{x:Type loc:Class}" ItemsSource="{Binding Students}">
            <StackPanel Orientation="Horizontal">
                <Image Margin="2" Source="{Binding ImagePath}">
                </Image>
                <TextBlock Margin="2" Text="{Binding Name}">
                </TextBlock>
            </StackPanel>
        </HierarchicalDataTemplate>
        <HierarchicalDataTemplate DataType="{x:Type loc:Student}">
            <StackPanel Orientation="Horizontal">
                <Image Margin="2" Source="{Binding ImagePath}">
                </Image>
                <TextBlock Margin="2" Text="{Binding Name}" ToolTip="{Binding ToolTip}">
                </TextBlock>
            </StackPanel>
        </HierarchicalDataTemplate>
    </TreeView.Resources>
</TreeView>

public bool IsExpanded
{
    get
    {
        return m_IsExpanded;
    }
    set
    {
        if (Equals(m_IsExpanded, value))
        {
            return;
        }

        m_IsExpanded = value;

        NotifyPropertyChanged("IsExpanded");
    }
}