按属性名称排序列表

Question

我编写了一个函数来在单击列标题时对 ListView 进行排序。我现在希望该功能适用​​于任何列。我的第一个想法是传递一个表示列中显示的属性的字符串，并使用if 或switch 按正确的属性进行排序，例如：

private bool sortOrder = false;
public void SortCol(string property)
{
    OUModel ou = ADRoot.Descendants().Where(node => node.IsSelected == true).FirstOrDefault() as OUModel;

    if (ou != null)
    {
        switch (property)
        {
            case "Name":
                if (sortOrder)
                {
                    ou.Computers = new List<RemoteComputer>(ou.Computers.OrderBy(c => c.Name));
                }
                else
                {
                    ou.Computers = new List<RemoteComputer>(ou.Computers.OrderByDescending(c => c.Name));
                }
                break;

            case "LastUpdated":
                if (sortOrder)
                {
                    ou.Computers = new List<RemoteComputer>(ou.Computers.OrderBy(c => c.LastUpdated));
                }
                else
                {
                    ou.Computers = new List<RemoteComputer>(ou.Computers.OrderByDescending(c => c.LastUpdated));
                }
                break;
                // etc...
        }
        sortOrder = !sortOrder;
    }
}

但这显然会变得相当冗长和重复。相反，我想知道我是否可以通过财产本身。但我试图从 XAML 传递属性类型（使用 Caliburn.Micro Actions），但不知道如何。

private bool sortOrder = false;
public void SortCol<T>(Func<RemoteComputer, T> property)
{
    OUModel ou = ADRoot.Descendants().Where(node => node.IsSelected == true).FirstOrDefault() as OUModel;

    if (ou != null)
    {
        if (sortOrder)
        {
            ou.Computers = new List<RemoteComputer>(ou.Computers.OrderBy(property));
        }
        else
        {
            ou.Computers = new List<RemoteComputer>(ou.Computers.OrderByDescending(property));
        }
        sortOrder = !sortOrder;
    }
}

XAML：

    <!-- Name Spaces
    xmlns:models="clr-namespace:MyProject.Models"
    xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
    xmlns:cal="http://www.caliburnproject.org"
    -->

    <!-- TreeView the ListView is bound to -->
    <TreeView x:Name="ADTree" ItemsSource="{Binding ADRoot.Children}">
    <!-- -->

    <ListView x:Name="ADComputers" ItemsSource="{Binding SelectedItem.Computers, ElementName=ADTree, Mode=TwoWay}" SelectionMode="Multiple" ItemContainerStyle="{DynamicResource RemoteComputerItem}">
        <ListView.View>
            <GridView>
                <GridViewColumn x:Name="Name" Width="120" DisplayMemberBinding="{Binding Name}">
                    <GridViewColumn.Header>
                        <GridViewColumnHeader x:Name="SortName" Content="Computer Name">
                            <i:Interaction.Triggers>
                                <i:EventTrigger EventName="Click">
                                    <cal:ActionMessage MethodName="SortCol">
     <!-- Trying to pass type here, but nested types are not supported. Don't know how else I can do this -->
                                        <cal:Parameter Value="{x:Type models:RemoteComputer.Name}" />
                                    </cal:ActionMessage>
                                </i:EventTrigger>
                            </i:Interaction.Triggers>
                        </GridViewColumnHeader>
                    </GridViewColumn.Header>
                </GridViewColumn>
                <!-- Other Columns -->
            </GridView>
        </ListView.View>
    </ListView>

类等：

class ADTreeViewModel : OUModel
{    
    public OUModel ADRoot { get; set; } = new OUModel(null, false); // <<< TreeView is bound to this, and ListView is bound to TreeView.SelectedItem.Computers
}

class OUModel : PropertyChangedBase, ITreeViewItemViewModel
{
    private List<RemoteComputer> computers = new List<RemoteComputer>();
    public List<RemoteComputer> Computers { get { return computers; } set { computers = value; NotifyOfPropertyChange(); } }
}

class RemoteComputer : PropertyChangedBase
{
    public string Name
    {
        get { return name; }
        set { name = value; NotifyOfPropertyChange(() => Name); }
    }

    // Shortening the other properties, but you get the idea...
    public IPAddress IP { //etc }
    public ComputerStatus Status { //etc }
    public DateTime LastUpdated { //etc }

    // and so on...
}

Answer 1

您不需要开关。如果您想按名称访问您的属性，您可以创建一个Expression 来构建一个Func

private bool sortOrder = false;
public void SortCol(string propName)
{
    OUModel ou = ADRoot.Descendants().Where(node => node.IsSelected == true).FirstOrDefault() as OUModel;

    if (ou != null)
    {
        if (sortOrder)
            ou.Computers = ou.Computers.OrderBy(GetProperty(propName)).ToList();
        else
            ou.Computers = ou.Computers.OrderByDescending(GetProperty(propName)).ToList();
        sortOrder = !sortOrder;
    }
}

// this method creates an Expression<Func<RemoteComputer,object>>
// and returning its compiled() resutl. Func<RemoteComputer,object>
// so you can use this `Func` in your orderBy methods.
public Func<T, object> GetProperty<T>(string propertyName)
{
// q =>
    ParameterExpression param = Expression.Parameter(typeof(T), "q");
// q.propertyName  
// for example : q.Name
    MemberExpression member = Expression.PropertyOrField(param, propertyName);
// change property type to object (because we want to use all posible types of our class peroperties or fields)
    var body = Expression.Convert(member, typeof(object));
// create Expression<Func<RemoteComputer,object>>
    var property = Expression.Lambda<Func<T, object>>(body, param);
// returns a Func<T,object>
    return property.Compile();
}

---

更新

此外，您可以使用此扩展类将 OrderBy 字符串支持添加到整个应用程序中的列表中。这也适用于 IQueryable 查询。

public static class OrderByExtentions
{
    public static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> list, string propertyName )
    {
        return list.OrderByDescending(GetPropertyFunc<T>(propertyName));
    }
    public static IQueryable<T> OrderByDescending<T>(this IQueryable<T> list, string propertyName)
    {
        return list.OrderByDescending(GetPropertyExpression<T>(propertyName));
    }
    public static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> list, string propertyName)
    {
        return list.OrderBy(GetPropertyFunc<T>(propertyName));
    }
    public static IQueryable<T> OrderBy<T>(this IQueryable<T> list, string propertyName)
    {
        return list.OrderBy(GetPropertyExpression<T>(propertyName));
    }
    private static Expression<Func<T, object>> GetPropertyExpression<T>(string propertyName)
    {
        ParameterExpression param = Expression.Parameter(typeof(T), "q");
        MemberExpression member = Expression.PropertyOrField(param, propertyName);
        var body = Expression.Convert(member, typeof(object));
        return Expression.Lambda<Func<T, object>>(body, param);
    }
    private static Func<T, object> GetPropertyFunc<T>(string propertyName)
    {
        return GetPropertyExpression<T>(propertyName).Compile();
    }
}

用法：

// eg. propName = "Name";

ou.Computers = ou.Computers.OrderByDescending(propName).ToList();

// or

ou.Computers = ou.Computers.OrderBy(propName).ToList();