我编写了一个函数，用于在单击列标题时对ListView进行排序。我现在希望该功能可用于任何列。我的第一个想法是传递一个字符串，该字符串代表要显示在列中的属性，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;
}
}
但这显然会变得很长且重复。相反，我想知道是否可以通过财产本身。但是我试图通过XAML（使用Caliburn.Micro Actions）传递属性类型，并且不知道如何实现。
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>
课程等
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...
}
答案 0 :(得分：1)
您不需要切换。如果您想按名称访问属性，则可以创建一个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();
}
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。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();